Percutaneous treatment of adult isthmic aortic coarctation: acute and long-term clinical and imaging outcome with a self-expandable uncovered nitinol stent.

Science.gov (United States)

Kische, Stephan; D'Ancona, Giuseppe; Stoeckicht, Yannik; Ortak, Jasmin; Elsässer, Albrecht; Ince, Hüseyin

2015-01-01

To present perioperative and long-term results of percutaneous treatment of adult isthmic coarctation of the aorta by means of a self-expandable closed-web uncovered nitinol stent (Sinus-XL, Optimed, Esslingen, Germany). Preoperative, perioperative, and long-term clinical and computed tomographic angiography data were collected and analyzed prospectively. A total of 52 consecutive patients were treated with the Sinus-XL stent. Mean age was 36.6 (21-67) years, peak invasive trans-coarctation of the aorta gradient was 54.7 ± 9.9 mm Hg, and upper body hypertension unresponsive to medical treatment was present in all patients. Mean stent diameter and length were 24.2 mm (22-28 mm) and 70.4 mm (40-80 mm), respectively. Eight patients (15.4%) required coarctation of the aorta predilatation. All patients underwent poststent dilatation with a noncompliant balloon. Postoperative peak gradient (3.3 ± 2.5 mm Hg) was reduced significantly (P stent collapse and secondary migration and documented stability in aortic diameter (18.3 ± 2.7 mm). Thirty patients (57.7%) were completely weaned-off antihypertensive medications and their use dropped from 2.6 to 0.9 drugs/patient (P self-expandable uncovered stent is safe and durable. The peculiar stent design maintains adequate localized radial strength over time with minimal trauma on the adjacent aortic wall and negligible device-related complications. Blood pressure control optimization is immediate and persistent even at long-term follow-up. © 2015 American Heart Association, Inc.

Self-Expanding Transcatheter Aortic Valve System for Symptomatic High-Risk Patients With Severe Aortic Stenosis

DEFF Research Database (Denmark)

Reichenspurner, Hermann; Schaefer, Andreas; Schäfer, Ulrich

2017-01-01

BACKGROUND: The CENTERA transcatheter heart valve (THV) is a low-profile, self-expanding nitinol valve made from bovine pericardial tissue that is 14-F compatible with a motorized delivery system allowing for repositionability. OBJECTIVES: The pivotal study evaluated safety and efficacy of this THV...... permanent pacemaker was implanted in 4.5% of patients receiving the THV (4.9% for patients at risk). CONCLUSIONS: The herein described THV is safe and effective at 30 days with low mortality, significant improvements in hemodynamic outcomes, and low incidence of adverse events. Of particular interest...... is the low incidence of permanent pacemaker implantations. (Safety and Performance Study of the Edwards CENTERA-EU Self-Expanding Transcatheter Heart Valve [CENTERA-2]; NCT02458560)....

Influence of Iliac Stenotic Lesions on Blood Flow Patterns Near a Covered Endovascular Reconstruction of the Aortic Bifurcation (CERAB) Stent Configuration

NARCIS (Netherlands)

Jebbink, Erik Groot; Engelhard, Stefan; Lajoinie, Guillaume; de Vries, Jean-Paul P.M.; Versluis, Michel; Reijnen, Michel M.P.J.

2017-01-01

Purpose: To investigate the effect of distal stenotic lesions on flow patterns near a covered endovascular reconstruction of the aortic bifurcation (CERAB) configuration used in the treatment of aortoiliac occlusive disease. Method: Laser particle image velocimetry measurements were performed using

Management of stent dislodgment in coarctoplasty of aorta with three overlapping self-expandable nitinol stents.

Science.gov (United States)

Ghazi, Payam; Haji-Zeinali, Ali-Mohammad

2010-01-01

We describe a case of native coarctation of aorta managed with three self-expandable nitinol stents. After balloon pre-dilation, the first and second stents were dislodged. The coarcted area was successfully treated with the third stent overlapped with the previous stents. During follow up (30 months), the patient was free of complications. It seems that implantation of multiple overlapping self-expandable stents in aortic coarctation patients, if needed, is safe and possible.

Development of tissue-engineered self-expandable aortic stent grafts (Bio stent grafts) using in-body tissue architecture technology in beagles.

Science.gov (United States)

Kawajiri, Hidetake; Mizuno, Takeshi; Moriwaki, Takeshi; Ishibashi-Ueda, Hatsue; Yamanami, Masashi; Kanda, Keiichi; Yaku, Hitoshi; Nakayama, Yasuhide

2015-02-01

In this study, we aimed to describe the development of tissue-engineered self-expandable aortic stent grafts (Bio stent graft) using in-body tissue architecture technology in beagles and to determine its mechanical and histological properties. The preparation mold was assembled by insertion of an acryl rod (outer diameter, 8.6 mm; length, 40 mm) into a self-expanding nitinol stent (internal diameter, 9.0 mm; length, 35 mm). The molds (n = 6) were embedded into the subcutaneous pouches of three beagles for 4 weeks. After harvesting and removing each rod, the excessive fragile tissue connected around the molds was trimmed, and thus tubular autologous connective tissues with the stent were obtained for use as Bio stent grafts (outer diameter, approximately 9.3 mm in all molds). The stent strut was completely surrounded by the dense collagenous membrane (thickness, ∼150 µm). The Bio stent graft luminal surface was extremely flat and smooth. The graft wall of the Bio stent graft possessed an elastic modulus that was almost two times higher than that of the native beagle abdominal aorta. This Bio stent graft is expected to exhibit excellent biocompatibility after being implanted in the aorta, which may reduce the risk of type 1 endoleaks or migration. © 2014 Wiley Periodicals, Inc.

One-Year Clinical Outcomes of Patients Presenting With ST-Segment Elevation Myocardial Infarction Caused by Bifurcation Culprit Lesions Treated With the Stentys Self-Apposing Coronary Stent: Results From the APPOSITION III Study.

Science.gov (United States)

Grundeken, Maik J; Lu, Huangling; Vos, Nicola; IJsselmuiden, Alexander; van Geuns, Robert-Jan; Wessely, Rainer; Dengler, Thomas; La Manna, Alessio; Silvain, Johanne; Montalescot, Gilles; Spaargaren, René; Tijssen, Jan G P; de Winter, Robbert J; Wykrzykowska, Joanna J; Amoroso, Giovanni; Koch, Karel T

2017-08-01

To investigate outcomes in patients with ST-segment elevation myocardial infarction (STEMI) after treatment with the Stentys self-apposing stent (Stentys SAS; Stentys S.A.) for bifurcation culprit lesions. The nitinol, self-expanding Stentys was initially developed as a dedicated bifurcation stent. The stent facilitates a provisional strategy by accommodating its diameter to both the proximal and distal reference diameters and offering an opportunity to "disconnect" the interconnectors, opening the stent toward the side branch. The APPOSITION (a post-market registry to assess the Stentys self-expanding coronary stent in acute myocardial infarction) III study was a prospective, multicenter, international, observational study including STEMI patients undergoing primary percutaneous coronary intervention (PCI) with the Stentys SAS. Clinical endpoints were evaluated and stratified by bifurcation vs non-bifurcation culprit lesions. From 965 patients included, a total of 123 (13%) were documented as having a bifurcation lesion. Target-vessel revascularization (TVR) rates were higher in the bifurcation subgroup (16.4% vs 10.0%; P=.04). Although not statistically significant, other endpoints were numerically higher in the bifurcation subgroup: major adverse cardiac events (MACE; 12.7% vs 8.8%), myocardial infarction (MI; 3.4% vs 1.8%), and definite/probable stent thrombosis (ST; 5.8% vs 3.1%). However, when postdilation was performed, clinical endpoints were similar between bifurcation and non-bifurcation lesions: MACE (8.7% vs 8.4%), MI (1.2% vs 0.7%), and definite/probable ST (3.7% vs 2.4%). The use of the Stentys SAS was safe and feasible for the treatment of bifurcation lesions in the setting of primary PCI for STEMI treatment with acceptable 1-year cardiovascular event rates, which improved when postdilation was performed.

Pacemaker dependency after transcatheter aortic valve implantation with the self-expanding Medtronic CoreValve System.

Science.gov (United States)

van der Boon, Robert M A; Van Mieghem, Nicolas M; Theuns, Dominic A; Nuis, Rutger-Jan; Nauta, Sjoerd T; Serruys, Patrick W; Jordaens, Luc; van Domburg, Ron T; de Jaegere, Peter P T

2013-09-30

To determine pacemaker (PM) dependency at follow-up visit in patients who underwent new permanent pacemaker implantation (PPI) following transcatheter aortic valve implantation (TAVI). Single center prospective observational study including 167 patients without previous PM implantation who underwent TAVI with the self-expanding Medtronic CoreValve System (MCS) between November 2005 and February 2011. PM dependency was defined by the presence of a high degree atrioventricular block (HDAVB; second [AV2] and third degree [AV3B]), or a slow (atrial fibrilation with slow response (n=1, 2.8%) and left bundle branch block (n=1, 2.8%). Long term follow-up was complete for all patients and ranged from 1 to 40 months (median (IQR): 11.5 (5.0-18.0 months). Of those patients with a HDAVB, 16 out of the 30 patients (53.3%) were PM independent at follow-up visit (complete or partial resolution of the AV conduction abnormality). Overall, 20 out of the 36 patients (55.6%) who received a new PM following TAVI were PM independent at follow-up. Partial and even complete resolution of peri-operative AV conduction abnormalities after MCS valve implantation occurred in more than half of the patients. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

Effect of aorto-iliac bifurcation and iliac stenosis on flow dynamics in an abdominal aortic aneurysm

Science.gov (United States)

Patel, Shivam; Usmani, Abdullah Y.; Muralidhar, K.

2017-06-01

Physiological flows in rigid diseased arterial flow phantoms emulating an abdominal aortic aneurysm (AAA) under rest conditions with aorto-iliac bifurcation and iliac stenosis are examined in vitro through 2D PIV measurements. Flow characteristics are first established in the model resembling a symmetric AAA with a straight outlet tube. The influence of aorto-iliac bifurcation and iliac stenosis on AAA flow dynamics is then explored through a comparison of the nature of flow patterns, vorticity evolution, vortex core trajectory and hemodynamic factors against the reference configuration. Specifically, wall shear stress and oscillatory shear index in the bulge portion of the models are of interest. The results of this investigation indicate overall phenomenological similarity in AAA flow patterns across the models. The pattern is characterized by a central jet and wall-bounded vortices whose strength increases during the deceleration phase as it moves forward. The central jet impacts the wall of AAA at its distal end. In the presence of an aorto-iliac bifurcation as well as iliac stenosis, the flow patterns show diminished strength, expanse and speed of propagation of the primary vortices. The positions of the instantaneous vortex cores, determined using the Q-function, correlate with flow separation in the bulge, flow resistance due to a bifurcation, and the break in symmetry introduced by a stenosis in one of the legs of the model. Time-averaged WSS in a healthy aorta is around 0.70 N m-2 and is lowered to the range ±0.2 N m-2 in the presence of the downstream bifurcation with a stenosed common iliac artery. The consequence of changes in the flow pattern within the aneurysm on disease progression is discussed.

Effect of aorto-iliac bifurcation and iliac stenosis on flow dynamics in an abdominal aortic aneurysm

International Nuclear Information System (INIS)

Patel, Shivam; Usmani, Abdullah Y; Muralidhar, K

2017-01-01

Physiological flows in rigid diseased arterial flow phantoms emulating an abdominal aortic aneurysm (AAA) under rest conditions with aorto-iliac bifurcation and iliac stenosis are examined in vitro through 2D PIV measurements. Flow characteristics are first established in the model resembling a symmetric AAA with a straight outlet tube. The influence of aorto-iliac bifurcation and iliac stenosis on AAA flow dynamics is then explored through a comparison of the nature of flow patterns, vorticity evolution, vortex core trajectory and hemodynamic factors against the reference configuration. Specifically, wall shear stress and oscillatory shear index in the bulge portion of the models are of interest. The results of this investigation indicate overall phenomenological similarity in AAA flow patterns across the models. The pattern is characterized by a central jet and wall-bounded vortices whose strength increases during the deceleration phase as it moves forward. The central jet impacts the wall of AAA at its distal end. In the presence of an aorto-iliac bifurcation as well as iliac stenosis, the flow patterns show diminished strength, expanse and speed of propagation of the primary vortices. The positions of the instantaneous vortex cores, determined using the Q -function, correlate with flow separation in the bulge, flow resistance due to a bifurcation, and the break in symmetry introduced by a stenosis in one of the legs of the model. Time-averaged WSS in a healthy aorta is around 0.70 N m −2 and is lowered to the range ±0.2 N m −2 in the presence of the downstream bifurcation with a stenosed common iliac artery. The consequence of changes in the flow pattern within the aneurysm on disease progression is discussed. (paper)

Effect of aorto-iliac bifurcation and iliac stenosis on flow dynamics in an abdominal aortic aneurysm

Energy Technology Data Exchange (ETDEWEB)

Patel, Shivam; Usmani, Abdullah Y; Muralidhar, K, E-mail: kmurli@iitk.ac.in [Department of Mechanical Engineering, Indian Institute of Technology Kanpur, Kanpur 208016 (India)

2017-06-15

Physiological flows in rigid diseased arterial flow phantoms emulating an abdominal aortic aneurysm (AAA) under rest conditions with aorto-iliac bifurcation and iliac stenosis are examined in vitro through 2D PIV measurements. Flow characteristics are first established in the model resembling a symmetric AAA with a straight outlet tube. The influence of aorto-iliac bifurcation and iliac stenosis on AAA flow dynamics is then explored through a comparison of the nature of flow patterns, vorticity evolution, vortex core trajectory and hemodynamic factors against the reference configuration. Specifically, wall shear stress and oscillatory shear index in the bulge portion of the models are of interest. The results of this investigation indicate overall phenomenological similarity in AAA flow patterns across the models. The pattern is characterized by a central jet and wall-bounded vortices whose strength increases during the deceleration phase as it moves forward. The central jet impacts the wall of AAA at its distal end. In the presence of an aorto-iliac bifurcation as well as iliac stenosis, the flow patterns show diminished strength, expanse and speed of propagation of the primary vortices. The positions of the instantaneous vortex cores, determined using the Q -function, correlate with flow separation in the bulge, flow resistance due to a bifurcation, and the break in symmetry introduced by a stenosis in one of the legs of the model. Time-averaged WSS in a healthy aorta is around 0.70 N m{sup −2} and is lowered to the range ±0.2 N m{sup −2} in the presence of the downstream bifurcation with a stenosed common iliac artery. The consequence of changes in the flow pattern within the aneurysm on disease progression is discussed. (paper)

Surgery for acute Type I aortic dissection without resection of supra-aortic entry sites leads to unfavourable aortic remodelling.

Science.gov (United States)

Heo, Woon; Song, Suk-Won; Lee, Kwang-Hun; Lee, Shin-Young; Kim, Tae-Hoon; Baek, Min-Young; Yoo, Kyung-Jong

2018-01-29

This study aimed to evaluate the impact of remnant re-entries in arch branches on postoperative change in the aortic arch and descending aortic diameters and the rate of major adverse aortic events. Between January 2010 and December 2016, 249 patients underwent surgery for acute Type I aortic dissection. Patients who underwent total arch replacement, had Marfan syndrome or had intramural haematoma were excluded. Seventy-two patients with predischarge and follow-up computed tomography scans were enrolled. Patients with and without re-entries in the arch branches after surgery were assigned to the supra-aortic entry (SAE, n = 21) and no supra-aortic entry (n = 51) groups, respectively. Diameters were measured at 7 levels: the innominate artery, left common carotid artery, left subclavian artery, 20 mm distal to the left subclavian artery, pulmonary artery bifurcation, coeliac axis and maximal diameter of the descending thoracic aorta. Growth rates at the levels of the pulmonary artery bifurcation and 20 mm distal to the left subclavian artery were significantly higher in the SAE group than in the no supra-aortic entry group. The rate of freedom from major adverse aortic events (annual growth >5 mm or maximal diameter of the descending thoracic aorta >50 mm) at 5 years was significantly higher in the no supra-aortic entry group than in the SAE group. Remnant SAE leads to unfavourable aortic remodelling after acute Type I aortic dissection repair. © The Author(s) 2018. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.

Bifurcation Mode of Relativistic and Charge-Displacement Self-Channeling

International Nuclear Information System (INIS)

BORISOV, A.B.; CAMERON, STEWART M.; LUK, TING S.; NELSON, THOMAS R.; VAN TASSLE, A.J.; SANTORO, J.; SCHROEDER, W.A.; DAI, Y.; LONGWORTH, J.W.; BOYER, K.; RHODES, C.K.

2000-01-01

Stable self-channeling of ultra-powerful (P 0 - 1 TW -1 PW) laser pulses in dense plasmas is a key process for many applications requiring the controlled compression of power at high levels. Theoretical computations predict that the transition zone between the stable and highly unstable regimes of relativistic/charge-displacement self-channeling is well characterized by a form of weakly unstable behavior that involves bifurcation of the propagating energy into two powerful channels. Recent observations of channel instability with femtosecond 248 nm pulses reveal a mode of bifurcation that corresponds well to these theoretical predictions. It is further experimentally shown that the use of a suitable longitudinal gradient in the plasma density can eliminate this unstable behavior and restore the efficient formation of stable channels

Primary Self-Expandable Nitinol Stent Placement in Focal Lesions of Infrarenal Abdominal Aorta: Long Term Results

International Nuclear Information System (INIS)

Lastovickova, Jarmila; Peregrin, Jan H.

2008-01-01

Purpose. To evaluate the technical and clinical success, safety and long term results of percutaneous transluminal angioplasty/self-expandable nitinol stent placement of infrarenal abdominal aorta focal lesions. Materials and Methods. Eighteen patients underwent PTA of focal atherosclerotic occlusive disease of distal abdominal aorta. Two symptomatic occlusions and 16 stenoses in 10 male and 8 female patients (mean age 68.2 years) were treated with primary self-expandable nitinol stent placement. Results. Primary self-expandable nitinol stent placement was technically successful in all 18 procedures; clinical success was achieved in 100% of patients. No complications associated with the procedure occurred. During the 49.4 months of mean follow up (range 3-96, 4 months) all treated aortic segments remained patent. Conclusions. Endovascular treatment (primary self-expandable nitinol stent placement) of focal atherosclerotic lesions of distal abdominal aorta is a safe method with excellent primary technical and clinical success rates and favourable Long term results

Mortality and complications after aortic bifurcated bypass procedures for chronic aortoiliac occlusive disease

DEFF Research Database (Denmark)

Bredahl, Kim; Jensen, Leif Panduro; Schroeder, Torben V

2015-01-01

skills, particularly because open surgery is increasingly used in those patients who are unsuitable for endovascular repair and hence technically more demanding. We assessed the early outcome after aortic bifurcated bypass procedures during two decades of growing endovascular activity and identified...... preoperative risk factors. METHODS: Data on patients with chronic limb ischemia were prospectively collected during a 20-year period (1993 to 2012). The data were obtained from the Danish Vascular Registry, assessed, and merged with data from The Danish Civil Registration System. RESULTS: We identified 3623...... aortobifemoral and 144 aortobiiliac bypass procedures. The annual caseload fell from 323 to 106 during the study period, but the 30-day mortality at 3.6% (95% confidence interval [CI], 3.0-4.1) and the 30-day major complication rate remained constant at 20% (95% CI, 18-21). Gangrene (odds ratio [OR], 3.3; 95% CI...

Abdominal aortic aneurysm neck remodeling after Anaconda stent graft implantation.

Science.gov (United States)

Vukovic, Elisabeth; Czerny, Martin; Beyersdorf, Friedhelm; Wolkewitz, Martin; Berezowski, Mikolaj; Siepe, Matthias; Blanke, Philipp; Rylski, Bartosz

2018-05-24

The aim of this study was to define how the proximal landing zone changes geometrically after endovascular abdominal aortic aneurysm repair (EVAR) with the Anaconda (Vascutek, Inchinnan, United Kingdom) stent graft. Among 230 patients who underwent Anaconda stent graft implantation between 2005 and 2014, we included 126 with adequate computed tomography (CT) image quality and follow-up. CT analysis entailed the geometric changes in the main body, proximal rings, and proximal landing zone. The median CT follow-up was 2.0 years (345.8 patients-years). The proximal portion of the main body ring system flattened within the first year after EVAR, resulting in an up to 30° increase in the upper ring's angle in 40% patients and up to 40° increase in 24% patients. One year after EVAR, the upper ring angle increase slowed down. Aortic diameter measured at the level of the upper and lower ring expanded by 2 to 4 mm within 1 year, but remained unchanged afterward. The main body migrated continuously down toward the aortic bifurcation, attaining an average 6-mm increase in the distance between the superior mesenteric artery and main body within 4 years. Freedom from endoleak type IA was 95 ± 2% and 93 ± 3% after 1 and 4 years, respectively. The Anaconda main body ring system in its proximal portion flattens within the first year after EVAR, leading to an increase of 2 to 4 mm in the proximal landing zone's aortic diameter. The main body migrates slowly but continuously down toward the aortic bifurcation. Copyright © 2018 Society for Vascular Surgery. Published by Elsevier Inc. All rights reserved.

Hybrid treatment of bullet embolism at the abdominal aortic bifurcation, complicated with thoracoabdominal aorta pseudoaneurysm and common iliac artery occlusion: case report

Directory of Open Access Journals (Sweden)

Patrick Bastos Metzger

2014-03-01

Full Text Available Embolization due to a firearm projectile entering the bloodstream is a rare event that is unlikely to be suspected during initial treatment of trauma patients. We describe and discuss a case of bullet embolism of the abdominal aortic bifurcation, complicated by a pseudoaneurysm of the thoracoabdominal aorta and occlusion of the right common iliac artery, but successfully treated using a combination of endovascular methods and conventional surgery.

Expanding indications for valve-sparing aortic root reconstruction: early and midterm results.

Science.gov (United States)

Valo, Johanna; Jokinen, Janne J; Kaarne, Markku; Ihlberg, Leo

2013-02-01

Valve-sparing aortic root reconstruction (VSRR) is an accepted method to treat patients with aortic root dilation. The role of the VSRR is less well defined for patients with bicuspid aortic valve, severe aortic valve insufficiency, congenital heart defects, and type A aortic dissection. We studied the clinical outcome of patients who underwent VSRR for expanded indications. Seventy-eight patients underwent VSRR between the 2005 and 2012. Seventy-two patients (92%) underwent reimplantation and 6 patients (8%) were operated on with the remodeling technique. The mean age was 51 ± 12 years (range 24 to 73). For 71 patients (91%), the operation was elective, and for 7 (9%; all with type A aortic dissection), on an emergency basis. Preoperatively, the degree of aortic insufficiency was graded as 2+ or greater for 27 patients (35%). Connective tissue disorder (Marfan or Loeys-Dietz), bicuspid aortic valve, or congenital heart disease was present in 15 (19%), 15 (19%), and 7 patients (9%), respectively. Concomitant aortic valve leaflet repair was performed for 39 patients (50%). The mean follow-up time was 2.4 ± 1.7 years (range, 0.1 to 7.0). Thirty-day mortality was zero. The rate of postoperative complications was low: stroke 3%, renal failure 3%, prosthesis infection 1%, and low cardiac output syndrome 1%. Survival was 100% at 1 year and 97% at 5 years. Freedom from recurrent aortic valve insufficiency (≥2+) during the follow-up was 94%. The midterm results of VSRR in terms of survival, freedom from recurrent aortic valve insufficiency, and the need for reoperation are excellent, even for high-risk patients. Copyright © 2013 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.

Outcomes for the Commercial Use of Self-Expanding Prostheses in Transcatheter Aortic Valve Replacement: A Report From the STS/ACC TVT Registry.

Science.gov (United States)

Sorajja, Paul; Kodali, Susheel; Reardon, Michael J; Szeto, Wilson Y; Chetcuti, Stanley J; Hermiller, James; Chenoweth, Sharla; Adams, David H; Popma, Jeffrey J

2017-10-23

The authors sought to compare the outcomes of commercial transcatheter aortic valve replacement (TAVR) with the repositionable Evolut R platform to those observed with the CoreValve device in the Society of Thoracic Surgeons (STS)/American College of Cardiology (ACC) Transcatheter Valve Therapy (TVT) Registry. TAVR continues to evolve, with rapid adoption of iterative changes for commercial practice. Insight into the outcomes of this adoption is needed. Patients in the TVT Registry who had TAVR using a 23-, 26-, or 29-mm self-expanding prosthesis were enrolled. Site-reported events for procedural, in-hospital, and 30-day outcomes were examined. Between January 2014 and April 2016, 9,616 patients underwent TAVR with a self-expanding prosthesis with data entered in the TVT Registry. Compared with patients treated with CoreValve TAVR, those who received Evolut R TAVR had a lower STS-PROM score (8.0 ± 5.4% vs. 8.7 ± 5.3%; p < 0.001), more iliofemoral access (91.6% vs. 89.2%; p < 0.001), and more frequently had conscious sedation (27.4% vs. 12.7%; p < 0.001). With Evolut R TAVR, there was less need for a second prosthesis (2.2% vs. 4.5%; p < 0.001), less device migration (0.2% vs. 0.6%; p = 0.01), a lower incidence of moderate/severe paravalvular regurgitation (post-procedure, 4.4% vs. 6.2%; p < 0.001), and shorter median hospital stay (4.0 vs. 5.0 days; p < 0.001). Patients treated with Evolut R TAVR had greater device success (96.3% vs. 94.9%; p = 0.001). At 30 days, Evolut R patients had both lower mortality (3.7% vs. 5.3%; p < 0.001) and less need for a pacemaker (18.3% vs. 20.1%; p = 0.03). Commercial adoption of the Evolut R platform is associated with significant improvements in acute outcomes for patients undergoing TAVR for aortic stenosis. Copyright © 2017 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

Percutaneous implantation of the first repositionable aortic valve prosthesis in a patient with severe aortic stenosis.

Science.gov (United States)

Buellesfeld, Lutz; Gerckens, Ulrich; Grube, Eberhard

2008-04-01

Percutaneous aortic valve replacement is a new less-invasive alternative for high-risk surgical candidates with aortic stenosis. However, the clinical experience is still limited, and the currently available 'first-generation devices' revealed technical shortcomings, such as lack of repositionability and presence of paravalvular leakages. We report the first-in-man experience with the new self-expanding Lotus Valve prosthesis composed of a nitinol frame with implemented bovine pericardial leaflets which is designed to address these issues, being repositionable and covered by a flexible membrane to seal paravalvular gaps. We implanted this prosthesis in a 93-year old patient presenting with severe symptomatic aortic stenosis (valve area: 0.6 cm(2)). Surgical valve replacement had been declined due to comorbidities. We used a retrograde approach for insertion of the 21-French Lotus catheter loaded with the valve prosthesis via surgical cut-down to the external iliac artery. Positioning of the valve was guided by transesophageal echo and supra-aortic angiograms. The prosthesis was successfully inserted and deployed within the calcified native valve. Echocardiography immediately after device deployment showed a significant reduction of the transaortic mean pressure gradient (32 to 9 mmHg; final valve area 1.7 cm(2)) without evidence of residual aortic regurgitation. The postprocedural clinical status improved from NYHA-IV to NYHA-II. These results remained unchanged up to the 3 month follow-up. Successful percutaneous aortic valve replacement can be performed using the new self-expanding and repositionable Lotus valve for treatment of high-risk patients with aortic valve stenosis. Further studies are mandatory to assess device safety and efficacy in larger patient populations. Copyright 2008 Wiley-Liss, Inc.

Induction of continuous expanding infrarenal aortic aneurysms in a large porcine animal model

DEFF Research Database (Denmark)

Kloster, Brian Ozeraitis; Lund, Lars; Lindholt, Jes S.

2015-01-01

BackgroundA large animal model with a continuous expanding infrarenal aortic aneurysm gives access to a more realistic AAA model with anatomy and physiology similar to humans, and thus allows for new experimental research in the natural history and treatment options of the disease. Methods10 pigs...

Degenerate Hopf bifurcation in a self-exciting Faraday disc dynamo

Indian Academy of Sciences (India)

Weiquan Pan

2017-05-31

May 31, 2017 ... Recently, self-exciting Faraday disk dynamo is also a topic of con- cern [16–20]. ..... Hopf bifurcation. (a) Projected on the x–z plane and (b) pro- ... Key Lab of Com- plex System Optimization and Big Data Processing. (No.

Time-Resolved Three-Dimensional Contrast-Enhanced Magnetic Resonance Angiography in Patients with Chronic Expanding and Stable Aortic Dissections

Directory of Open Access Journals (Sweden)

Michael Trojan

2017-01-01

Full Text Available Objective. To prospectively evaluate our hypothesis that three-dimensional time-resolved contrast-enhanced magnetic resonance angiography (TR-MRA is able to detect hemodynamic alterations in patients with chronic expanding aortic dissection compared to stable aortic dissections. Materials and Methods. 20 patients with chronic or residual aortic dissection in the descending aorta and patent false lumen underwent TR-MRA of the aorta at 1.5 T and repeated follow-up imaging (mean follow-up 5.4 years. 7 patients showed chronic aortic expansion and 13 patients had stable aortic diameters. Regions of interest were placed in the nondissected ascending aorta and the false lumen of the descending aorta at the level of the diaphragm (FL-diaphragm level resulting in respective time-intensity curves. Results. For the FL-diaphragm level, time-to-peak intensity and full width at half maximum were significantly shorter in the expansion group compared to the stable group (p=0.027 and p=0.003, and upward and downward slopes of time-intensity curves were significantly steeper (p=0.015 and p=0.005. The delay of peak intensity in the FL-diaphragm level compared to the nondissected ascending aorta was significantly shorter in the expansion group compared to the stable group (p=0.01. Conclusions. 3D TR-MRA detects significant alterations of hemodynamics within the patent false lumen of chronic expanding aortic dissections compared to stable aortic dissections.

Self-expandable nitinol stent placement in homocysteinemic porcine aorta

Directory of Open Access Journals (Sweden)

Luís Henrique Gil França

2008-01-01

Full Text Available PURPOSE: To compare aortic intimal thickening of normal and hyperhomocysteinemic pigs (induced with a methionine-rich diet following placement of a self-expanding nitinol stent. METHODS: Eighteen Macau pigs were used. They were older than eight weeks in age and had an average weight of 30 kg. Pigs were randomly divided into two groups. The first, Group C (control, was fed a regular diet, and the second group, Group M, was fed a methionine-rich diet for 30 days to induce hyperhomocysteinemia. The self-expandable nitinol stents were 25mm in length and 8 mm in diameter after expansion. Blood samples were collected to measure total cholesterol, triglycerides, HDL and homocysteine concentrations. All animals were subjected to angiography. Thirty days after the procedure, the animals were sacrificed, and the abdominal aorta was removed for histological and digital morphometry analysis. RESULTS: Under microscopic evaluation, the intima was significantly thicker in Group C than in Group M. When groups were compared by digital morphometric analysis, intimal thickening of the vessel wall was higher in Group C than in Group M. There was no significant change in total cholesterol, triglycerides or HDL concentrations in either group. In group C the levels of plasma homocysteine ranged from 14,40 to 16,73µmol/l; in Group M, plasma homocysteine levels ranged from 17.47 to 59.80 µmol/l after 30 days of a methionine-rich diet. CONCLUSION: Compared to normal pigs, less intimal hyperplasia was observed in the abdominal aortas of hyperhomocysteinemic pigs thirty days after the insertion of a self-expandable nitinol stent.

Square Stent: A New Self-Expandable Endoluminal Device and Its Applications

International Nuclear Information System (INIS)

Pavcnik, Dusan; Uchida, Barry; Timmermans, Hans; Keller, Frederick S.; Roesch, Josef

2001-01-01

The square stent is a new, simply constructed, self-expanding device that has recently been described. Compared with other stents, the square stent has a minimal amount of metal and thus requires a smaller-diameter catheter for introduction. Despite the small amount of metal present, the square stent has adequate expansile force. We have been evaluating the square stent for various interventional applications. In addition to the basic square stent, combinations of square stents and coverings for square stents were developed and evaluated to expand its uses and indications. One of the coverings tested is a new biomaterial: small intestinal submucosa (SIS). This paper will discuss the various applications of the square stent, which include a retrievable inferior vena cava filter, vascular occluder, graft adapter, and venous and aortic valves. In addition, we will review the important properties of SIS as a covering for the square stent

Self-Expandable Stenting over a Stent Graft for the Exclusion of a Carotid Stump: Troubleshooting for Device Incompatibility

International Nuclear Information System (INIS)

Youn, Sung Won; Kim, Ho Kyun; Do, Jin Kook; Kim, Young Whan

2011-01-01

Carotid stump, the blind remnant of an occluded internal carotid artery, can be a potential source of microemboli, and warrants its exclusion from the vascular lumen to prevent the recurrence of a microembolism. In a 69-year-old male with a symptomatic carotid stump and acute angle between left common carotid artery and aortic arch, a 7-Fr. shuttle sheath was scarcely placed into the left carotid artery but the 7-mm-diameter stent-graft-loading balloon could not be inserted into the 7-Fr. shuttle sheath. With the mounting a stent graft over a 5-mm balloon, the balloon-expandable stent graft was unfolded. The self-expandable stent was placed over the stent graft, and an 8-mm balloon was subsequently expanded. Self-expanding stenting can be useful for troubleshooting in a case of device incompatibility coming from the different calibers of the external and common carotid arteries for the successful exclusion of a symptomatic carotid stump.

Self-Expandable Stenting over a Stent Graft for the Exclusion of a Carotid Stump: Troubleshooting for Device Incompatibility

Energy Technology Data Exchange (ETDEWEB)

Youn, Sung Won; Kim, Ho Kyun [Dept. of Radiology, Catholic University of Daegu School of Medicine, Daegu (Korea, Republic of); Do, Jin Kook [Dept. of Neurology, Catholic University of Daegu School of Medicine, Daegu (Korea, Republic of); Kim, Young Whan [Dept. of Radiology, University College of Medicine, Daegu (Korea, Republic of)

2011-12-15

Carotid stump, the blind remnant of an occluded internal carotid artery, can be a potential source of microemboli, and warrants its exclusion from the vascular lumen to prevent the recurrence of a microembolism. In a 69-year-old male with a symptomatic carotid stump and acute angle between left common carotid artery and aortic arch, a 7-Fr. shuttle sheath was scarcely placed into the left carotid artery but the 7-mm-diameter stent-graft-loading balloon could not be inserted into the 7-Fr. shuttle sheath. With the mounting a stent graft over a 5-mm balloon, the balloon-expandable stent graft was unfolded. The self-expandable stent was placed over the stent graft, and an 8-mm balloon was subsequently expanded. Self-expanding stenting can be useful for troubleshooting in a case of device incompatibility coming from the different calibers of the external and common carotid arteries for the successful exclusion of a symptomatic carotid stump.

Transapical aortic valve implantation using a Symetis Acurate self-expandable bioprosthesis: initial outcomes of 10 patients.

Science.gov (United States)

Misterski, Marcin; Puślecki, Mateusz; Grygier, Marek; Olasińska-Wiśniewska, Anna; Lesiak, Maciej; Araszkiewicz, Aleksander; Perek, Barłomiej; Choręziak, Aneta; Lindner, Jacek; Komosa, Anna; Buczkowski, Piotr; Ligowski, Marcin; Katarzyński, Sławomir; Jemielity, Marek

2017-06-01

Transapical aortic valve implantation (TA-AVI) has been widely introduced for treatment of patients with severe aortic stenosis in the last decade. Here we report our first clinical experience with 10 patients using the second-generation transapical Symetis Acurate TA aortic valve designed for transapical implantation. To evaluate the results of transapical access in transcatheter aortic valve implantation (TAVI) among patients with unsuitable vascular access. All patients had been assessed by a local heart team and were disqualified from surgical aortic valve replacement (AVR) and the transfemoral TAVI approach. Mean age was 75.4 ±3.9 years (range: 68-80), with 20% being female. Logistic EuroSCORE (European System for Cardiac Operative Risk Evaluation) and STS (Society of Thoracic Surgeons) were 15.4 ±8.9% and 20.5 ±4.5%, respectively. All implantations were performed successfully in the intra-annular and subcoronary position. There were no conversions to surgical AVR. All patients survived 30-day follow-up. No strokes or transient ischemic attacks were reported. There was no need for pacemaker implantation and none of the patients demonstrated moderate or significant paravalvular leakage. The mean aortic gradients improved significantly from a baseline of 57.0 ±19.2 mm Hg to a 30-day value of 14.2 ±4.1 mm Hg. Our initial clinical results indicate satisfactory functionality in patients after trans-apical implantation of the Symetis Acurate aortic valve. The procedure of implantation seems to be straightforward and may be considered in patients in whom a transfemoral approach is not a good option.

Bifurcation Regulations Governed by Delay Self-Control Feedback in a Stochastic Birhythmic System

Science.gov (United States)

Ma, Zhidan; Ning, Lijuan

2017-12-01

We aim to investigate bifurcation behaviors in a stochastic birhythmic van der Pol (BVDP) system subjected to delay self-control feedback. First, the harmonic approximation is adopted to drive the delay self-control feedback to state variables without delay. Then, Fokker-Planck-Kolmogorov (FPK) equation and stationary probability density function (SPDF) for amplitude are obtained by applying stochastic averaging method. Finally, dynamical scenarios of the change of delay self-control feedback as well as noise that markedly influence bifurcation performance are observed. It is found that: the big feedback strength and delay will suppress the large amplitude limit cycle (LC) while the relatively big noise strength facilitates the large amplitude LC, which imply the proposed regulation strategies are feasible. Interestingly enough, the inner LC is never destroyed due to noise. Furthermore, the validity of analytical results was verified by Monte Carlo simulation of the dynamics.

Development of a New Intravascular Low-Profile Device for Exclusion of Aortic Aneurysm: An Experimental Pilot Study

International Nuclear Information System (INIS)

Strecker, Ernst-Peter; Haberstroh, Joerg; Boos, Irene; Metz, Stephan; Langer, Mathias; Moliner, Manuel Maynar

2004-01-01

Purpose: To present a new intravascular device for the treatment of aorto-iliac aneurysms. Methods: This new device was tested in five dogs with abdominal aortic aneurysm created experimentally by overdilation of a balloon-expandable stent with a 16 or 18 mm wide PTA balloon catheter. The design of the device is based on a self-expanding aortic stent which consists of two stretchable circular frames filled with a textile Dacron mesh membrane that is suspended horizontally into the infrarenal abdominal aorta proximally to the aneurysm. The frames are part of a preshaped double helical structure that is introduced longitudinally through a catheter in a parallel fashion and forming the desired shape at the vessel site to be occluded. Two iliac stent-grafts are introduced in a low-profile status through the membrane sealing the aneurysm sac and holding the stent-grafts in place. After stent-graft expansion, a new bifurcation located more proximally than the natural one is created. The follow-up of the dogs was performed clinically and angiographically, and specimens were evaluated histomorphologically. Results: The membrane device can be introduced through a 9 Fr vascular sheath. Technical success was achieved in four of five dogs. Nine of ten stent-grafts could be fixed securely within the membrane, thus preventing dislocation. Aneurysms were excluded immediately, and blood flow to the external iliac arteries was restored by the stent-grafts. At 6-9 months follow-up of technically successful implanted devices, there were no endoleaks, no migration, no stenoses at contact sites between the implant material and vascular wall, and no stenosis or occlusion of the stent-grafts. At microscopic evaluation, the interspace between the membranes was filled with thrombotic material, thus ensuring exclusion of the aneurysm. Conclusion: This new device was found to be flexible, low profile and useful in excluding abdominal aortic aneurysm in the experimental setting

Aortic anomalies in an adolescent with the Williams' elfin facies syndrome

International Nuclear Information System (INIS)

Williams, R.L.; Azouz, E.M.

1984-01-01

An adolescent with classical Williams' syndrome who presented with hypertensive encephalopathy is described. He had the unusual combination of supravalvular aortic stenosis, long segment coarctation of the aorta, aortic hypoplasia and a high bifurcation of the abdominal aorta. Surgical resection of the coarctation was required; however, the patient has remained moderately hypertensive. The aortic anomalies in this syndrome are reviewed and their frequency and importance examined. (orig.)

Self-Organized Patterns Induced by Neimark-Sacker, Flip and Turing Bifurcations in a Discrete Predator-Prey Model with Lesie-Gower Functional Response

Directory of Open Access Journals (Sweden)

Feifan Zhang

2017-06-01

Full Text Available The formation of self-organized patterns in predator-prey models has been a very hot topic recently. The dynamics of these models, bifurcations and pattern formations are so complex that studies are urgently needed. In this research, we transformed a continuous predator-prey model with Lesie-Gower functional response into a discrete model. Fixed points and stability analyses were studied. Around the stable fixed point, bifurcation analyses including: flip, Neimark-Sacker and Turing bifurcation were done and bifurcation conditions were obtained. Based on these bifurcation conditions, parameters values were selected to carry out numerical simulations on pattern formation. The simulation results showed that Neimark-Sacker bifurcation induced spots, spirals and transitional patterns from spots to spirals. Turing bifurcation induced labyrinth patterns and spirals coupled with mosaic patterns, while flip bifurcation induced many irregular complex patterns. Compared with former studies on continuous predator-prey model with Lesie-Gower functional response, our research on the discrete model demonstrated more complex dynamics and varieties of self-organized patterns.

Incidence, feasibility and outcome of percutaneous coronary intervention after transcatheter aortic valve implantation with a self-expanding prosthesis. Results from a single center experience.

Science.gov (United States)

Allali, Abdelhakim; El-Mawardy, Mohamed; Schwarz, Bettina; Sato, Takao; Geist, Volker; Toelg, Ralph; Richardt, Gert; Abdel-Wahab, Mohamed

2016-09-01

Percutaneous coronary intervention (PCI) after transcatheter aortic valve implantation (TAVI) can become technically challenging after implantation of the self-expanding Medtronic CoreValve (MCV) device, which completely covers the aortic root. The aim of this study was to report on the incidence, feasibility and outcome of PCI after TAVI with the MCV device. Between 2007 and 2014, all patients subjected to PCI after MCV implantation in a single-center institutional TAVI database were retrospectively identified. Clinical, angiographic and procedural characteristics were reviewed and analyzed. We identified a total of 17 patients (5.7%) treated with 24 PCI procedures for 29 lesions at a median of 17.7months (range 1-72) after MCV implantation. The mean age was 79.7±6.8years and the mean logistic EuroSCORE was 30.3%±18.9%. Nine procedures were performed for patients with acute coronary syndrome. 89.6% of the treated lesions were of type B2/C and 79.3% were de novo ones. A median of one guiding catheter was necessary to intubate the target coronary ostium (range 1-10) and 95% of the lesions on the left coronary artery were treated through a Judkins catheter. In one primary PCI for STEMI the intubation of the right coronary ostium was not successful. Final procedural success was obtained in 95.8%, and peri-procedural death occurred in one patient. The need for PCI after MCV is not uncommon and is mostly related to coronary artery disease progression. PCI after MCV is usually feasible and safe, but coronary intubation in an emergency setting can be challenging. Copyright © 2016 Elsevier Inc. All rights reserved.

Topography of Aortic Bifurcation in a Black Kenyan Population ...

African Journals Online (AJOL)

After removal of abdominal viscera, peritoneum, fibrofatty connective tissue, inferior vena cava was removed to expose the termination of abdominal aorta. Vertebral level, angle and asymmetry of bifurcation were recorded. Data were analysed by SPSS version 17.0 for windows and are presented in tables and bar charts.

Bifurcation analysis for a discrete-time Hopfield neural network of two neurons with two delays and self-connections

International Nuclear Information System (INIS)

Kaslik, E.; Balint, St.

2009-01-01

In this paper, a bifurcation analysis is undertaken for a discrete-time Hopfield neural network of two neurons with two different delays and self-connections. Conditions ensuring the asymptotic stability of the null solution are found, with respect to two characteristic parameters of the system. It is shown that for certain values of these parameters, Fold or Neimark-Sacker bifurcations occur, but Flip and codimension 2 (Fold-Neimark-Sacker, double Neimark-Sacker, resonance 1:1 and Flip-Neimark-Sacker) bifurcations may also be present. The direction and the stability of the Neimark-Sacker bifurcations are investigated by applying the center manifold theorem and the normal form theory

Induction of continuous expanding infrarenal aortic aneurysms in a large porcine animal model

DEFF Research Database (Denmark)

Kloster, Brian Ozeraitis; Lund, Lars; Lindholt, Jes S.

2015-01-01

frequent complication was a neurological deficit in the lower limbs. ConclusionIn pigs it’s possible to induce continuous expanding AAA’s based upon proteolytic degradation and pathological flow, resembling the real life dynamics of human aneurysms. Because the lumbars are preserved, it’s also a potential......BackgroundA large animal model with a continuous expanding infrarenal aortic aneurysm gives access to a more realistic AAA model with anatomy and physiology similar to humans, and thus allows for new experimental research in the natural history and treatment options of the disease. Methods10 pigs......, hereafter the pigs were euthanized for inspection and AAA wall sampling for histological analysis. ResultsIn group A, all pigs developed continuous expanding AAA’s with a mean increase in AP-diameter to 16.26 ± 0.93 mm equivalent to a 57% increase. In group B the AP-diameters increased to 11.33 ± 0.13 mm...

Factors leading to tracheobronchial self-expandable metallic stent fracture.

Science.gov (United States)

Chung, Fu-Tsai; Lin, Shu-Min; Chen, Hao-Cheng; Chou, Chun-Liang; Yu, Chih-Teng; Liu, Chien-Ying; Wang, Chun-Hua; Lin, Horng-Chyuan; Huang, Chien-Da; Kuo, Han-Pin

2008-11-01

This retrospective study was to determine factors that contribute to self-expandable metallic stent fracture in patients with tracheobronchial disease. From 2001 to 2006, 139 patients (age, 62.1 +/- 15.4 years; range, 23-87 years) with benign (n = 62) and malignant (n = 77) tracheobronchial disease received 192 Ultraflex (Boston Scientific, Natick, Mass) self-expandable metallic stents (98 in patients with benign disease and 94 in patients with malignant disease). Seventeen fractured self-expandable metallic stents were found; the incidence was 12.2% (17/139 patients) among patients with tracheobronchial disease. Tortuous airway (odds ratio, 4.06; 95% confidence interval, 1.04-18.34; P = .04) independently predicted self-expandable metallic stent fracture. Most self-expandable metallic stent fractures (64.7%, 11/17) were detected 500 to 1000 days after self-expandable metallic stent implantation. Clinical presentations for patients with fractured self-expandable metallic stents included dyspnea exacerbation (70.6%, 12/17) and cough (23.5%, 4/17). Self-expandable metallic stent fracture is not uncommon in patients with tracheobronchial disease. Tortuous airway is an independent predictor for it. Although management of the fractured self-expandable metallic stent in our study was feasible and safe, self-expandable metallic stents should be restricted to a more select population.

Transluminal endovascular stent-graft for the treatment of aortic aneurysms

Energy Technology Data Exchange (ETDEWEB)

Lee, Do Yun; Chang, Byung Chul; Shim, Won Heum; Cho, Seung Yun; Chung, Nam Sik; Kwon, Hyuk Moon; Lee, Young Joon; Lee, Jong Tae [Yonsei University College of Medicine, Seoul (Korea, Republic of)

1995-09-15

The standard treatment for aortic aneurysms is surgical replacement with a prosthetic graft. Currently there is great interest in endoluminal intervention for treatment of aortic aneurysm. The purpose of this study was to evaluate the safety and effectiveness of endoluminally placed Stent-graft for the treatment of aortic aneurysms. Transluminal endovascular Stent-graft placements were attempted in 9 patients with infra-renal aortic aneurysms(n 6), thoracic aortic aneurysm(n = 1), and aortic dissection(n = 2). The endovascular Stent-grafts were custom-designed for each patient and were constructed of self-expandable modified Gianturco Stents covered with polytetrafluroethylene. The Stent-grafts were introduced through a 16-18 French sheath and expanded to 17-30 mm in diameter. The endovascular therapy was performed using a common femoral artery cutdown with local anesthesia. The endovascular Stent-graft deployment was achieved in 7 of 9 patients. Two cases failed deployment of the Stent-graft due to iliac artery stenosis and tortousity. There were complete thrombosis of the thoracic and infra-renal aortic aneurysm surround the Stent-graft in 3 patients, and persistent leak with partial thrombosis in 2. Two patients with aortic dissection were successfully treated by obliteration of entry tears. There were no major complication associated with Stent-graft placement. These preliminary results show that transluminal endovascular Stent-grafts offer great promise and good results. Further investigation is needed to establish its long-term safety and efficacy.

Transluminal endovascular stent-graft for the treatment of aortic aneurysms

International Nuclear Information System (INIS)

Lee, Do Yun; Chang, Byung Chul; Shim, Won Heum; Cho, Seung Yun; Chung, Nam Sik; Kwon, Hyuk Moon; Lee, Young Joon; Lee, Jong Tae

1995-01-01

The standard treatment for aortic aneurysms is surgical replacement with a prosthetic graft. Currently there is great interest in endoluminal intervention for treatment of aortic aneurysm. The purpose of this study was to evaluate the safety and effectiveness of endoluminally placed Stent-graft for the treatment of aortic aneurysms. Transluminal endovascular Stent-graft placements were attempted in 9 patients with infra-renal aortic aneurysms(n 6), thoracic aortic aneurysm(n = 1), and aortic dissection(n = 2). The endovascular Stent-grafts were custom-designed for each patient and were constructed of self-expandable modified Gianturco Stents covered with polytetrafluroethylene. The Stent-grafts were introduced through a 16-18 French sheath and expanded to 17-30 mm in diameter. The endovascular therapy was performed using a common femoral artery cutdown with local anesthesia. The endovascular Stent-graft deployment was achieved in 7 of 9 patients. Two cases failed deployment of the Stent-graft due to iliac artery stenosis and tortousity. There were complete thrombosis of the thoracic and infra-renal aortic aneurysm surround the Stent-graft in 3 patients, and persistent leak with partial thrombosis in 2. Two patients with aortic dissection were successfully treated by obliteration of entry tears. There were no major complication associated with Stent-graft placement. These preliminary results show that transluminal endovascular Stent-grafts offer great promise and good results. Further investigation is needed to establish its long-term safety and efficacy

A case of complete double aortic arch visualized by transthoracic echocardiography.

Science.gov (United States)

Saito, Naka; Kato, Shingo; Saito, Noritaka; Nakachi, Tatsuya; Fukui, Kazuki; Iwasawa, Tae; Kosuge, Masami; Kimura, Kazuo

2017-08-01

A case of double aortic arch that was well visualized using transthoracic echocardiography is reported. A 38-year-old man underwent transthoracic echocardiography for the evaluation of dyspnea. A suprasternal view of transthoracic echocardiography showed the ascending aorta bifurcate to left and right aortic arches, with blood flow from the ascending aorta to bilateral aortic arches. The diagnosis of right side-dominant double aortic arch was made, and the patient's symptom was conceivably related to compression of the trachea due to a vascular ring. This report indicates the potential usefulness of transthoracic echocardiography for noninvasive detection of double aortic arch in adults. © 2017, Wiley Periodicals, Inc.

Comparison of self-expandable and balloon-expanding stents for hybrid ductal stenting in hypoplastic left heart complex.

Science.gov (United States)

Goreczny, Sebastian; Qureshi, Shakeel A; Rosenthal, Eric; Krasemann, Thomas; Nassar, Mohamed S; Anderson, David R; Morgan, Gareth J

2017-07-01

We aimed to compare the procedural and mid-term performance of a specifically designed self-expanding stent with balloon-expandable stents in patients undergoing hybrid palliation for hypoplastic left heart syndrome and its variants. The lack of specifically designed stents has led to off-label use of coronary, biliary, or peripheral stents in the neonatal ductus arteriosus. Recently, a self-expanding stent, specifically designed for use in hypoplastic left heart syndrome, has become available. We carried out a retrospective cohort comparison of 69 neonates who underwent hybrid ductal stenting with balloon-expandable and self-expanding stents from December, 2005 to July, 2014. In total, 43 balloon-expandable stents were implanted in 41 neonates and more recently 47 self-expanding stents in 28 neonates. In the balloon-expandable stents group, stent-related complications occurred in nine patients (22%), compared with one patient in the self-expanding stent group (4%). During follow-up, percutaneous re-intervention related to the ductal stent was performed in five patients (17%) in the balloon-expandable stent group and seven patients (28%) in self-expanding stents group. Hybrid ductal stenting with self-expanding stents produced favourable results when compared with the results obtained with balloon-expandable stents. Immediate additional interventions and follow-up re-interventions were similar in both groups with complications more common in those with balloon-expandable stents.

Attractors, bifurcations, & chaos nonlinear phenomena in economics

CERN Document Server

Puu, Tönu

2003-01-01

The present book relies on various editions of my earlier book "Nonlinear Economic Dynamics", first published in 1989 in the Springer series "Lecture Notes in Economics and Mathematical Systems", and republished in three more, successively revised and expanded editions, as a Springer monograph, in 1991, 1993, and 1997, and in a Russian translation as "Nelineynaia Economicheskaia Dinamica". The first three editions were focused on applications. The last was differ­ ent, as it also included some chapters with mathematical background mate­ rial -ordinary differential equations and iterated maps -so as to make the book self-contained and suitable as a textbook for economics students of dynamical systems. To the same pedagogical purpose, the number of illus­ trations were expanded. The book published in 2000, with the title "A ttractors, Bifurcations, and Chaos -Nonlinear Phenomena in Economics", was so much changed, that the author felt it reasonable to give it a new title. There were two new math­ ematics ch...

Study design and rationale of the 'Balloon-Expandable Cobalt Chromium SCUBA Stent versus Self-Expandable COMPLETE-SE Nitinol Stent for the Atherosclerotic ILIAC Arterial Disease (SENS-ILIAC Trial) Trial': study protocol for a randomized controlled trial.

Science.gov (United States)

Choi, Woong Gil; Rha, Seung Woon; Choi, Cheol Ung; Kim, Eung Ju; Oh, Dong Joo; Cho, Yoon Hyung; Park, Sang Ho; Lee, Seung Jin; Hur, Ae Yong; Ko, Young Guk; Park, Sang Min; Kim, Ki Chang; Kim, Joo Han; Kim, Min Woong; Kim, Sang Min; Bae, Jang Ho; Bong, Jung Min; Kang, Won Yu; Seo, Jae Bin; Jung, Woo Yong; Cho, Jang Hyun; Kim, Do Hoi; Ahn, Ji Hoon; Kim, Soo Hyun; Jang, Ji Yong

2016-06-25

The self-expandable COMPLETE™ stent (Medtronic) has greater elasticity, allowing it to regain its shape after the compression force reduces, and has higher trackability, thus is easier to maneuver through tortuous vessels, whereas the balloon-expandable SCUBA™ stent (Medtronic) has higher radial stiffness and can afford more accurate placement without geographic miss, which is important in aortoiliac bifurcation lesions. To date, there have been no randomized control trials comparing efficacy and safety between the self-expanding stent and balloon-expandable stent in advanced atherosclerotic iliac artery disease. The purpose of our study is to examine primary patency (efficacy) and incidence of stent fracture and geographic miss (safety) between two different major representative stents, the self-expanding nitinol stent (COMPLETE-SE™) and the balloon-expanding cobalt-chromium stent (SCUBA™), in stenotic or occlusive iliac arterial lesions. This trial is designed as a prospective, randomized, multicenter trial to demonstrate a noninferiority of SCUBA™ stent to COMPLETE-SE™ stent following balloon angioplasty in iliac arterial lesions, and a total of 280 patients will be enrolled. The primary end point of this study is the rate of primary patency in the treated segment at 12 months after intervention as determined by catheter angiography, computed tomography angiography, or duplex ultrasound. The SENS-ILIAC trial will give powerful insight into whether the stent choice according to deployment mechanics would impact stent patency, geographic miss, or stent fracture in patients undergoing stent implantation in iliac artery lesions. National Institutes of Health Clinical Trials Registry (ClinicalTrials.gov identifier: NCT01834495 ), registration date: May 8, 2012.

Transcatheter valve-in-valve implantation due to severe aortic regurgitation in a degenerated aortic homograft

DEFF Research Database (Denmark)

Olsen, Lene Kjaer; Engstrøm, Thomas; Søndergaard, Lars

2009-01-01

Transcatheter aortic valve implantation (TAVI) in severe aortic stenosis has proven to be a feasible and effective treatment modality for inoperable patients. Until now, neither aortic regurgitation nor degenerated bioprostheses has been an indication for TAVI. However, this article reports...... a successful valve-in-valve implantation of a CoreValve aortic valve prosthesis through the right subclavian artery in a case of severe aortic regurgitation within a degenerated aortic homograft. The case exemplifies the possibilities of expanding the indications for TAVI, as well as other vascular access...

Percutaneous implantation of the CoreValve aortic valve prosthesis in patients at high risk or rejected for surgical valve replacement: Clinical evaluation and feasibility of the procedure in the first 30 patients in the AMC-UvA

NARCIS (Netherlands)

Baan, J.; Yong, Z. Y.; Koch, K. T.; Henriques, J. P. S.; Bouma, B. J.; de Hert, S. G.; van der Meulen, J.; Tijssen, J. G. P.; Piek, J. J.; de Mol, B. A. J. M.

2010-01-01

Objective. To report the feasibility, safety and efficacy of percutaneous aortic valve implantation (PAVI) with the CoreValve self-expanding aortic valve bioprosthesis in elderly patients with aortic valve stenosis who are rejected for surgery or have a high surgical risk.Methods. PAVI using the

Self-expanding/shrinking structures by 4D printing

Science.gov (United States)

Bodaghi, M.; Damanpack, A. R.; Liao, W. H.

2016-10-01

The aim of this paper is to create adaptive structures capable of self-expanding and self-shrinking by means of four-dimensional printing technology. An actuator unit is designed and fabricated directly by printing fibers of shape memory polymers (SMPs) in flexible beams with different arrangements. Experiments are conducted to determine thermo-mechanical material properties of the fabricated part revealing that the printing process introduced a strong anisotropy into the printed parts. The feasibility of the actuator unit with self-expanding and self-shrinking features is demonstrated experimentally. A phenomenological constitutive model together with analytical closed-form solutions are developed to replicate thermo-mechanical behaviors of SMPs. Governing equations of equilibrium are developed for printed structures based on the non-linear Green-Lagrange strain tensor and solved implementing a finite element method along with an iterative incremental Newton-Raphson scheme. The material-structural model is then applied to digitally design and print SMP adaptive lattices in planar and tubular shapes comprising a periodic arrangement of SMP actuator units that expand and then recover their original shape automatically. Numerical and experimental results reveal that the proposed planar lattice as meta-materials can be employed for plane actuators with self-expanding/shrinking features or as structural switches providing two different dynamic characteristics. It is also shown that the proposed tubular lattice with a self-expanding/shrinking mechanism can serve as tubular stents and grippers for bio-medical or piping applications.

Vibrations analysis and bifurcations in the self-sustained electromechanical system with multiple functions

International Nuclear Information System (INIS)

Yamapi, R.; Moukam Kakmeni, F.M.; Aziz-Alaoui, M.A.

2005-07-01

We consider in this paper the dynamics of the self-sustained electromechanical system with multiple functions, consisting of an electrical Rayleigh-Duffing oscillator, magnetically coupled with linear mechanical oscillators. The averaging and the balance harmonic method are used to and the amplitudes of the oscillatory states respectively in the autonomous and non-autonomous cases, and analyze the condition in which the quenching of self-sustained oscillations appears. The effects of the number of linear mechanical oscillators on the behavior of the model are discussed. Various bifurcation structures, the stability chart and the variation of the Lyapunov exponent are obtained, using numerical simulations of the equations of motion. (author)

Simultaneous rota-stenting and transcatheter aortic valve implantation for patients with heavily calcified coronary stenosis and aortic stenosis

Directory of Open Access Journals (Sweden)

Yung-Tsai Lee

2016-09-01

Full Text Available Given that coronary artery disease (CAD in octogenarians undergoing transcatheter aortic valve implantation (TAVI often presents with more complex lesions and extensive calcification, rotational atherectomy (RA may be needed in some cases before stenting. However, data regarding the feasibility and safety of simultaneous RA during TAVI using the Medtronic CoreValve (MCV; Medtronic, Minneapolis, MN, USA system are lacking. Three out of 107 (2.8% patients (2 females, average age 85.6 years, mean aortic valve area 0.5 cm2, mean left ventricular ejection fraction 39%, mean Logistic EuroScore 70%, with complex, heavily calcified coronary stenosis, and severe valvular aortic stenosis (AS were treated with TAVI and RA due to high surgical risk. After balloon valvuloplasty, all coronary lesions were successfully treated with RA and stenting, immediately followed by transfemoral TAVI with a self-expandable MCV. Our data suggested that in the very elderly patients with severe and heavily calcified CAD and AS who were turned down for cardiac surgery, RA and stenting followed by TAVI may be performed successfully in a combined, single-stage procedure.

Dynamics and Physiological Roles of Stochastic Firing Patterns Near Bifurcation Points

Science.gov (United States)

Jia, Bing; Gu, Huaguang

2017-06-01

Different stochastic neural firing patterns or rhythms that appeared near polarization or depolarization resting states were observed in biological experiments on three nervous systems, and closely matched those simulated near bifurcation points between stable equilibrium point and limit cycle in a theoretical model with noise. The distinct dynamics of spike trains and interspike interval histogram (ISIH) of these stochastic rhythms were identified and found to build a relationship to the coexisting behaviors or fixed firing frequency of four different types of bifurcations. Furthermore, noise evokes coherence resonances near bifurcation points and plays important roles in enhancing information. The stochastic rhythms corresponding to Hopf bifurcation points with fixed firing frequency exhibited stronger coherence degree and a sharper peak in the power spectrum of the spike trains than those corresponding to saddle-node bifurcation points without fixed firing frequency. Moreover, the stochastic firing patterns changed to a depolarization resting state as the extracellular potassium concentration increased for the injured nerve fiber related to pathological pain or static blood pressure level increased for aortic depressor nerve fiber, and firing frequency decreased, which were different from the physiological viewpoint that firing frequency increased with increasing pressure level or potassium concentration. This shows that rhythms or firing patterns can reflect pressure or ion concentration information related to pathological pain information. Our results present the dynamics of stochastic firing patterns near bifurcation points, which are helpful for the identification of both dynamics and physiological roles of complex neural firing patterns or rhythms, and the roles of noise.

Esophagorespiratory fistula: treatment with self-expanding covered stent

International Nuclear Information System (INIS)

Zang Jian; Dou Yongchong; Wang Zheng; Kong Jian

2002-01-01

Objective: To evaluate self-expanding covered stent in the management of esophagorespiratory fistula. Methods: A self-expanding esophageal covered stent was implanted under fluoroscopic guidance in 13 patients with esophagorespiratory fistula. In this series patients aged 31-73 years (60.2 years in average). All patients had a pre-procedure fast of 6-41 days (17.3 days in average), in which 12 patients had pulmonary infection. Results: All fistulas were excluded and swallowing function was restored. No stend-related complication was observed. Pulmonary infection was managed in 10 patients out of 13. The mean survived time was 33.3 wks (1-178 wks) in follow-up. Conclusion: Covered self-expanding stent implantation is a safe and effective treatment of ERF

Stent implantation for the treatment of wide-necked aneurysms located at internal carotid artery bifurcation

International Nuclear Information System (INIS)

Xing Ming; Yang Pengfei; Huang Qinghai; Zhao Wenyuan; Hong Bo; Xu Yi; Liu Jianmin

2012-01-01

Objective: To preliminarily evaluate the feasibility, safety and efficacy of stent placement for the treatment of wide-necked aneurysms located at internal carotid artery bifurcation. Methods: Eleven patients with wide-necked aneurysms located at internal carotid artery bifurcation, who were encountered during the period from Jan. 2004 to Dec. 2010 in hospital, were collected. A total of 16 intracranial aneurysms were detected, of which 11 were wide-necked and were located at internal carotid artery bifurcation. The diameters of the aneurysms ranged from 2.5 mm to 18 mm. Individual stent type and stenting technique was employed for each patient. Follow-up at 1, 3, 6 and 12 months after the procedure was conducted. Results: A total of 11 different stents were successfully deployed in the eleven patients. The stents included balloon expandable stent (n=1) and self-expanding stent (n=10). According to Raymond grading for the immediate occlusion of the aneurysm, grade Ⅰ (complete obliteration) was obtained in 4, grade Ⅱ (residual neck) in 2 and grade Ⅲ (residual aneurysm) in 5 cases. No procedure-related complications occurred. At the time of discharge, the modified Rankin score was 0-1 in the eleven patients. During the follow-up period lasting for 1-108 months, all the patients were in stable condition and no newly-developed neurological dysfunction or bleeding observed. Follow-up examination with angiography (1-48 months) showed that the aneurysms were cured (no visualization) in 4 cases, improved in 2 cases and in stable condition in one case. Conclusion: For the treatment of wide-necked aneurysms located at internal carotid artery bifurcation, stent implantation is clinically feasible, safe and effective. Further studies are required to evaluate its long-term efficacy. (authors)

Midterm to long-term safety and efficacy of self-expandable nitinol stent implantation for coarctation of aorta in adults.

Science.gov (United States)

Haji Zeinali, Ali Mohammad; Sadeghian, Mohammad; Qureshi, Shakeel A; Ghazi, Payam

2017-09-01

Endovascular treatment of coarctation of aorta (CoA) by self-expandable Nitinol stents is one of the recognized treatment methods and may be an alternative to surgery or balloon-expandable stent implantation for CoA but there is little information about midterm to long term results of self-expandable stents. Sixty-two patients with CoA (40 men), with a mean age of 30.7 ± 11 years, (range 17-63 years) underwent stent implantation with Optimed self-expandable Nitinol stents between 2005 and 2014. Successful outcome was defined as peak systolic pressure gradient ≤20 mmHg after stent implantation. The patients were followed-up clinically and by echocardiography and in patients, in whom there was suspicion of recoarctation, CT angiography or recatheterization was performed. 65 stents were successfully implanted in all 62 patients. Peak systolic pressure gradient decreased from mean 62.4 ± 18 mmHg (range 35-100 mmHg) to mean 2.8 ± 5 mmHg (range 0-15 mmHg; P Stent displacement occurred in 3 patients during the procedure. These were managed successfully by an overlapping second stent. None of the patients had major complications such as aortic dissection, rupture, or vascular access problems. In follow up, only three patients had recoarctation, and two of these were managed successfully by balloon redilation or further stenting 16 and 18 months after the first procedure and one patient refused reintervention. There were two deaths, unrelated to the procedure, 12 and 78 months after the initial intervention. Follow-up of a mean of 45.5 ± 17 months (range 12-105 months) demonstrated no evidence of aneurysm formation or stent fracture. Self-expandable nitinol stents for the treatment of native and recurrent CoA is safe and has good efficacy with acceptable midterm to long-term outcome. © 2017 Wiley Periodicals, Inc.

A multiscale modelling approach to understand atherosclerosis formation: A patient-specific case study in the aortic bifurcation

Science.gov (United States)

Alimohammadi, Mona; Pichardo-Almarza, Cesar; Agu, Obiekezie; Díaz-Zuccarini, Vanessa

2017-01-01

Atherogenesis, the formation of plaques in the wall of blood vessels, starts as a result of lipid accumulation (low-density lipoprotein cholesterol) in the vessel wall. Such accumulation is related to the site of endothelial mechanotransduction, the endothelial response to mechanical stimuli and haemodynamics, which determines biochemical processes regulating the vessel wall permeability. This interaction between biomechanical and biochemical phenomena is complex, spanning different biological scales and is patient-specific, requiring tools able to capture such mathematical and biological complexity in a unified framework. Mathematical models offer an elegant and efficient way of doing this, by taking into account multifactorial and multiscale processes and mechanisms, in order to capture the fundamentals of plaque formation in individual patients. In this study, a mathematical model to understand plaque and calcification locations is presented: this model provides a strong interpretability and physical meaning through a multiscale, complex index or metric (the penetration site of low-density lipoprotein cholesterol, expressed as volumetric flux). Computed tomography scans of the aortic bifurcation and iliac arteries are analysed and compared with the results of the multifactorial model. The results indicate that the model shows potential to predict the majority of the plaque locations, also not predicting regions where plaques are absent. The promising results from this case study provide a proof of concept that can be applied to a larger patient population. PMID:28427316

Sequential transcatheter aortic valve implantation due to valve dislodgement - a Portico valve implanted over a CoreValve bioprosthesis.

Science.gov (United States)

Campante Teles, Rui; Costa, Cátia; Almeida, Manuel; Brito, João; Sondergaard, Lars; Neves, José P; Abecasis, João; M Gabriel, Henrique

2017-03-01

Transcatheter aortic valve implantation (TAVI) has become an important treatment in high surgical risk patients with severe aortic stenosis (AS), whose complications need to be managed promptly. The authors report the case of an 86-year-old woman presenting with severe symptomatic AS, rejected for surgery due to advanced age and comorbidities. The patient underwent a first TAVI, with implantation of a Medtronic CoreValve ® , which became dislodged and migrated to the ascending aorta. Due to the previous balloon valvuloplasty, the patient's AS became moderate, and her symptoms improved. After several months, she required another intervention, performed with a St. Jude Portico ® repositionable self-expanding transcatheter aortic valve. There was a good clinical response that was maintained at one-year follow-up. The use of a self-expanding transcatheter bioprosthesis with repositioning features is a solution in cases of valve dislocation to avoid suboptimal positioning of a second implant, especially when the two valves have to be positioned overlapping or partially overlapping each other. Copyright © 2017 Sociedade Portuguesa de Cardiologia. Publicado por Elsevier España, S.L.U. All rights reserved.

Self-Expanding, Tough Biodegradable Elastomers for Wound Stasis

Science.gov (United States)

2015-08-06

the civilian setting, with no effective therapies available at point of injury. We previously reported that a self- expanding polyurethane foam...setting, with no effective therapies available at point of injury. We previously reported that a self-expanding polyurethane foam significantly...care in accor- dance with the Guide of the Care and Use of Laboratory Ani- mals (Health, 2011 #17). 2.2. Instrumentation and monitoring All swine (n

The JUPITER registry: 1-year results of transapical aortic valve implantation using a second-generation transcatheter heart valve in patients with aortic stenosis.

Science.gov (United States)

Silaschi, Miriam; Treede, Hendrik; Rastan, Ardawan J; Baumbach, Hardy; Beyersdorf, Friedhelm; Kappert, Utz; Eichinger, Walter; Rüter, Florian; de Kroon, Thomas L; Lange, Rüdiger; Ensminger, Stephan; Wendler, Olaf

2016-11-01

Transcatheter aortic valve replacement (TAVR) is an established therapy for patients with aortic stenosis (AS) at high surgical risk. The JenaValve™ is a second-generation, self-expanding transcatheter heart valve (THV), implanted through transapical access (TA). During stent deployment, a specific 'clipping-mechanism' engages native aortic valve cusps for fixation. We present 1-year outcomes of the JUPITER registry, a post-market registry of the JenaValve for TA-TAVR. The JUPITER registry is a prospective, multicentre, uncontrolled and observational European study to evaluate the long-term safety and effectiveness of the Conformité Européenne-marked JenaValve THV. A total of 180 patients with AS were enrolled between 2012 and 2014. End-points were adjudicated in accordance with the valve academic research consortium document no. 1 definitions. The mean age was 80.4 ± 5.9 years and the mean logistic European system for cardiac operative risk evaluation I 21.2 ± 14.7%. The procedure was successful in 95.0% (171/180), implantation of a second THV (valve-in-valve) was performed in 2.2% (4/180) and conversion to surgical aortic valve replacement (SAVR) was necessary in 2.8% (5/180). No annular rupture or coronary ostia obstruction occurred. Two patients required SAVR after the day of index procedure (1.1%). All-cause mortality at 30 days was 11.1% (20/180), being cardiovascular in 7.2% (13/180). A major stroke occurred in 1.1% (2/180) at 30 days, no additional major strokes were observed during 1 year. All-cause mortality after 30 days was 13.1% (21/160) and combined efficacy at 1 year was 80.8% (122/151). At 1-year follow-up, no patient presented with more than moderate paravalvular leakage, while 2 patients (3.2%) showed moderate, 12 (19.0%) mild and 49 (82.4%) trace/none paravalvular regurgitation. In a high-risk cohort of patients undergoing TA-TAVR for AS, the use of the JenaValve THV is safe and effective. In patients at higher risk for coronary ostia

Expanding Sex-Role Definitions by Self-Discovery.

Science.gov (United States)

Kahn, Sharon E.; Greenberg, Leslie S.

1980-01-01

Counselors who stimulate client self-discovery may help these clients experience undeveloped parts of themselves and expand their definitions of themselves and their sex-role possibilities. Stimulation methods actively involve clients in the exploration of sex-role concerns to change restrictive self-concepts. (Author)

Sixth International Symposium on Bifurcations and Instabilities in Fluid Dynamics (BIFD2015)

DEFF Research Database (Denmark)

Bar-Yoseph, P. Z.; Brøns, Morten; Gelfgat, A.

2016-01-01

dynamics and remain a challenge for experimental, theoretical and computational studies. Examples of prototypical hydrodynamic instabilities are the Rayleigh–Bénard, Taylor–Couette, Bénard–Marangoni, Rayleigh–Taylor, and Kelvin–Helmholtz instabilities. A fundamental understanding of bifurcation patterns...... diseases, such as atherosclerotic and vulnerable plaques, abdominal aortic aneurisms, carotid artery disease, and pulmonary embolisms and implications for vascular interventions such as grafting and stenting. The collection of papers in this issue is a selection of the presentations given at the Sixth...

Functional Self-Expandable Metal Stents in Biliary Obstruction

Science.gov (United States)

Kwon, Chang-Il; Ko, Kwang Hyun; Hahm, Ki Baik

2013-01-01

Biliary stents are widely used not only for palliative treatment of malignant biliary obstruction but also for benign biliary diseases. Each plastic stent or self-expandable metal stent (SEMS) has its own advantages, and a proper stent should be selected carefully for individual condition. To compensate and overcome several drawbacks of SEMS, functional self-expandable metal stent (FSEMS) has been developed with much progress so far. This article looks into the outcomes and defects of each stent type for benign biliary stricture and describes newly introduced FSEMSs according to their functional categories. PMID:24143314

Percutaneous aortic valve implantation of the Medtronic CoreValve self-expanding valve prosthesis via left subclavian artery access: the first case report in Greece.

Science.gov (United States)

Karavolias, George K; Georgiadou, Panagiota; Houri, Mazen; Sbarouni, Eftihia; Thomopoulou, Sofia; Tsiapras, Dimitrios; Smirli, Anna; Balanika, Marina; Voudris, Vassilis

2010-01-01

This case report describes a percutaneous aortic valve implantation with the Medtronic CoreValve selfexpanding valve prosthesis in a patient with severe aortic stenosis. The approach was made via the left subclavian artery because of the lack of femoral vessel access. The patient was a 78-year-old female with breathlessness on minimal effort, a recent hospitalisation due to pulmonary oedema, and frequent episodes of pre-syncope; surgical valve replacement had been ruled out. The prosthetic valve was successfully implanted with mild paravalvular aortic regurgitation. At 30 days, the patient's clinical condition had significantly improved, with excellent functioning of the aortic valve prosthesis.

Bifurcation theory for hexagonal agglomeration in economic geography

CERN Document Server

Ikeda, Kiyohiro

2014-01-01

This book contributes to an understanding of how bifurcation theory adapts to the analysis of economic geography. It is easily accessible not only to mathematicians and economists, but also to upper-level undergraduate and graduate students who are interested in nonlinear mathematics. The self-organization of hexagonal agglomeration patterns of industrial regions was first predicted by the central place theory in economic geography based on investigations of southern Germany. The emergence of hexagonal agglomeration in economic geography models was envisaged by Krugman. In this book, after a brief introduction of central place theory and new economic geography, the missing link between them is discovered by elucidating the mechanism of the evolution of bifurcating hexagonal patterns. Pattern formation by such bifurcation is a well-studied topic in nonlinear mathematics, and group-theoretic bifurcation analysis is a well-developed theoretical tool. A finite hexagonal lattice is used to express uniformly distri...

Defining Electron Bifurcation in the Electron-Transferring Flavoprotein Family.

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Garcia Costas, Amaya M; Poudel, Saroj; Miller, Anne-Frances; Schut, Gerrit J; Ledbetter, Rhesa N; Fixen, Kathryn R; Seefeldt, Lance C; Adams, Michael W W; Harwood, Caroline S; Boyd, Eric S; Peters, John W

2017-11-01

Electron bifurcation is the coupling of exergonic and endergonic redox reactions to simultaneously generate (or utilize) low- and high-potential electrons. It is the third recognized form of energy conservation in biology and was recently described for select electron-transferring flavoproteins (Etfs). Etfs are flavin-containing heterodimers best known for donating electrons derived from fatty acid and amino acid oxidation to an electron transfer respiratory chain via Etf-quinone oxidoreductase. Canonical examples contain a flavin adenine dinucleotide (FAD) that is involved in electron transfer, as well as a non-redox-active AMP. However, Etfs demonstrated to bifurcate electrons contain a second FAD in place of the AMP. To expand our understanding of the functional variety and metabolic significance of Etfs and to identify amino acid sequence motifs that potentially enable electron bifurcation, we compiled 1,314 Etf protein sequences from genome sequence databases and subjected them to informatic and structural analyses. Etfs were identified in diverse archaea and bacteria, and they clustered into five distinct well-supported groups, based on their amino acid sequences. Gene neighborhood analyses indicated that these Etf group designations largely correspond to putative differences in functionality. Etfs with the demonstrated ability to bifurcate were found to form one group, suggesting that distinct conserved amino acid sequence motifs enable this capability. Indeed, structural modeling and sequence alignments revealed that identifying residues occur in the NADH- and FAD-binding regions of bifurcating Etfs. Collectively, a new classification scheme for Etf proteins that delineates putative bifurcating versus nonbifurcating members is presented and suggests that Etf-mediated bifurcation is associated with surprisingly diverse enzymes. IMPORTANCE Electron bifurcation has recently been recognized as an electron transfer mechanism used by microorganisms to maximize

Stability and Hopf Bifurcation of a Reaction-Diffusion Neutral Neuron System with Time Delay

Science.gov (United States)

Dong, Tao; Xia, Linmao

2017-12-01

In this paper, a type of reaction-diffusion neutral neuron system with time delay under homogeneous Neumann boundary conditions is considered. By constructing a basis of phase space based on the eigenvectors of the corresponding Laplace operator, the characteristic equation of this system is obtained. Then, by selecting time delay and self-feedback strength as the bifurcating parameters respectively, the dynamic behaviors including local stability and Hopf bifurcation near the zero equilibrium point are investigated when the time delay and self-feedback strength vary. Furthermore, the direction of the Hopf bifurcation and the stability of bifurcating periodic solutions are obtained by using the normal form and the center manifold theorem for the corresponding partial differential equation. Finally, two simulation examples are given to verify the theory.

Detailed investigation of the bifurcation diagram of capacitively coupled Josephson junctions in high-Tc superconductors and its self similarity

Science.gov (United States)

Hamdipour, Mohammad

2018-04-01

We study an array of coupled Josephson junction of superconductor/insulator/superconductor type (SIS junction) as a model for high temperature superconductors with layered structure. In the current-voltage characteristics of this system there is a breakpoint region in which a net electric charge appear on superconducting layers, S-layers, of junctions which motivate us to study the charge dynamics in this region. In this paper first of all we show a current voltage characteristics (CVC) of Intrinsic Josephson Junctions (IJJs) with N=3 Junctions, then we show the breakpoint region in that CVC, then we try to investigate the chaos in this region. We will see that at the end of the breakpoint region, behavior of the system is chaotic and Lyapunov exponent become positive. We also study the route by which the system become chaotic and will see this route is bifurcation. Next goal of this paper is to show the self similarity in the bifurcation diagram of the system and detailed analysis of bifurcation diagram.

Bifurcation and Fractal of the Coupled Logistic Map

Science.gov (United States)

Wang, Xingyuan; Luo, Chao

The nature of the fixed points of the coupled Logistic map is researched, and the boundary equation of the first bifurcation of the coupled Logistic map in the parameter space is given out. Using the quantitative criterion and rule of system chaos, i.e., phase graph, bifurcation graph, power spectra, the computation of the fractal dimension, and the Lyapunov exponent, the paper reveals the general characteristics of the coupled Logistic map transforming from regularity to chaos, the following conclusions are shown: (1) chaotic patterns of the coupled Logistic map may emerge out of double-periodic bifurcation and Hopf bifurcation, respectively; (2) during the process of double-period bifurcation, the system exhibits self-similarity and scale transform invariability in both the parameter space and the phase space. From the research of the attraction basin and Mandelbrot-Julia set of the coupled Logistic map, the following conclusions are indicated: (1) the boundary between periodic and quasiperiodic regions is fractal, and that indicates the impossibility to predict the moving result of the points in the phase plane; (2) the structures of the Mandelbrot-Julia sets are determined by the control parameters, and their boundaries have the fractal characteristic.

Treatment of intracranial wide neck aneurysm with neuroform self-expanding stent combined with spring coils

International Nuclear Information System (INIS)

Bai Weixing; Jiang Xifeng; Li Tianxiao; Zhai Shuiting; Xue Jiangyu; Wang Ziliang; Cao Huicun

2008-01-01

Objective: To evaluate the preliminary experience of the combined self-expanding neurovascular stent (Neuroform stent) with detachable coils in the management of intracranial wide neck aneurysms. Methods: Self-expanding neurovascular stents with detachable coils were used in treating 27 intracranial wide neck aneurysms of 25 patients including cavernous segment ICA aneurysms in 3, ophthalmic arterial anemysm in 1, PcomA in 18, AcomA in 2, MCAM1 in 1, MCA bifurcation in 1, and basilar trunk in 1. Among them, 2 cases consisted of multi-aneurysms, 2 aneurysms coincide with absolute wide neck (> 4 mm) and 6 with comparatively wide neck (> 7 mm). Nemoform stents were deployed across the neck of aneurysm and detachable coils were released to embolize the aneurysm through stent mesh. Results: Twenty-six Neuroform stents were successfully deployed in 25 patients including 4 Neuroform II stents, and 22 Neurofom III stents(all combined with spring coils). Total occlusion was achieved in 7 patients with residual neck in 9 nearly complete occlusion and partial occlusion in 11. 2 patients were rebleeding and other 2 showed intra-stent thrombosis during the operations. The latter 2 included 1 with post-operative limb paraplegia and 1 died. Still another 1 had transient ischemic attack after the operation. Twenty-three patient recovered well. Twenty-four patients were under clinical followed up from 0.5 to 28 months with an average of 10.8 months. There was no bleeding. Three patients were angiographically followed up for 3-6 months after the procedure, with only 1 case of in-stent thrombosis and no change in other 2 aneurysms with neck remnant. Conclusions: The Neuroform stent is technically feasible and safe for treating intracranial wide neck aneurysms unsuitable for clipping because of its prevention for coil protruding into parent artery. The long term effect still need to be further investigated. (authors)

Propagation of aortic dissection and visceral artery compromise. Three-dimensional analysis on CT angiography

International Nuclear Information System (INIS)

Minamiguchi, Hiroki

2003-01-01

The purpose of this study was to clarify the patterns of the propagation of aortic dissection with quantitative data from CT angiography and to verify the relationship between the propagation of aortic dissection and visceral artery compromise. The subjects were 67 cases (48 men, 19 women) with acute and subacute aortic dissection extending from the descending thoracic aorta to the aortic bifurcation. The mean age is 56.5±12.3 years old (range 34 to 80 years). Eight axial levels of the trunk of right pulmonary artery, left inferior pulmonary vein, coronary sinus, celiac axis, the orifice of superior mesenteric artery (SMA), the orifice of right real artery, the orifice of left renal artery and the orifice of inferior mesenteric artery were submitted to investigate the propagation of aortic dissection. The true lumen central angle was calculated in each level. The axial distance, branch angle difference and true distance between SMA and bilateral renal arteries were calculated. The trajectory of aortic dissection propagation from descending thoracic aorta to aortic bifurcation could be divided into two types of linear dissection type (n=41) and spiral dissection type (n=26). The latter were further subdivided into clockwise rotation type (n=14) and counter-clockwise rotation type (n=12). Younger age was significantly associated with the spiral dissection type as compared to older age (p=0.030). The spiral dissection type propagation pattern was found predominantly from the descending thoracic aorta to celiac axis, while at more distal levels linear type dissection was more common. The blood flow of SMA and celiac axis came from the true lumen or both lumens in all cases but single case from false lumen. The incidence (19.4%) of the right renal blood flow supplied from false lumen was lower than that (37.3%) of the left one supplied from false lumen. The shorter distance and the less angle difference between SMA and right renal artery than between SMA and left renal

Factors Affecting Optimal Aortic Remodeling After Thoracic Endovascular Aortic Repair of Type B (IIIb) Aortic Dissection

Energy Technology Data Exchange (ETDEWEB)

Chen, I-Ming [National Yang Ming University, Institute of Clinical Medicine, School of Medicine (China); Chen, Po-Lin; Huang, Chun-Yang [National Yang Ming University, Department of Medicine, School of Medicine (China); Weng, Shih-Hsien; Chen, Wei-Yuan; Shih, Chun-Che, E-mail: ccshih@vghtpe.gov.tw [National Yang Ming University, Institute of Clinical Medicine, School of Medicine (China)

2017-05-15

PurposeThe purpose of this study was to determine factors associated with entire aortic remodeling after thoracic endovascular aortic repair (TEVAR) in patients with type B dissection.Materials and MethodsThe patients with type B (IIIb) dissections who underwent TEVAR from 2006 to 2013 with minimum of 2 years of follow-up computed tomography data were retrospectively reviewed. Based on the status of false lumen remodeling of entire aorta, patients were divided into three groups: complete regression, total thrombosis, and inadequate regression with patent abdominal false lumen.ResultsA total of 90 patients (72 males, 18 females; mean age 56.6 ± 16.4 years) were included and divided into the complete regression (n = 22), total thrombosis (n = 18), and inadequate regression (n = 50) groups. Multivariate logistic regression analysis indicated that dissection extension to iliac arteries, increased preoperative number of dissection tear over abdominal aorta, and decreased preoperative abdominal aorta bifurcation true lumen ratio, as compared between the inadequate and complete regression groups, were associated with a persistent false lumen (odds ratio = 33.33, 2.304, and 0.021; all, p ≤ 0.012). Comparison of 6, 12, and 24 months postoperative data revealed no significant differences at any level, suggesting that the true lumen area ratio might not change after 6 months postoperatively.ConclusionsIncreased preoperative numbers of dissection tear around the abdominal visceral branches, dissection extension to the iliac arteries, and decreased preoperative true lumen area ratio of abdominal aorta are predictive of entire aortic remodeling after TEVAR in patients with type B dissection.Level of EvidenceIII.

Factors Affecting Optimal Aortic Remodeling After Thoracic Endovascular Aortic Repair of Type B (IIIb) Aortic Dissection

International Nuclear Information System (INIS)

Chen, I-Ming; Chen, Po-Lin; Huang, Chun-Yang; Weng, Shih-Hsien; Chen, Wei-Yuan; Shih, Chun-Che

2017-01-01

PurposeThe purpose of this study was to determine factors associated with entire aortic remodeling after thoracic endovascular aortic repair (TEVAR) in patients with type B dissection.Materials and MethodsThe patients with type B (IIIb) dissections who underwent TEVAR from 2006 to 2013 with minimum of 2 years of follow-up computed tomography data were retrospectively reviewed. Based on the status of false lumen remodeling of entire aorta, patients were divided into three groups: complete regression, total thrombosis, and inadequate regression with patent abdominal false lumen.ResultsA total of 90 patients (72 males, 18 females; mean age 56.6 ± 16.4 years) were included and divided into the complete regression (n = 22), total thrombosis (n = 18), and inadequate regression (n = 50) groups. Multivariate logistic regression analysis indicated that dissection extension to iliac arteries, increased preoperative number of dissection tear over abdominal aorta, and decreased preoperative abdominal aorta bifurcation true lumen ratio, as compared between the inadequate and complete regression groups, were associated with a persistent false lumen (odds ratio = 33.33, 2.304, and 0.021; all, p ≤ 0.012). Comparison of 6, 12, and 24 months postoperative data revealed no significant differences at any level, suggesting that the true lumen area ratio might not change after 6 months postoperatively.ConclusionsIncreased preoperative numbers of dissection tear around the abdominal visceral branches, dissection extension to the iliac arteries, and decreased preoperative true lumen area ratio of abdominal aorta are predictive of entire aortic remodeling after TEVAR in patients with type B dissection.Level of EvidenceIII.

Bifurcation analysis of nephron pressure and flow regulation

DEFF Research Database (Denmark)

Barfred, Mikael; Mosekilde, Erik; Holstein-Rathlou, N.-H.

1996-01-01

One- and two-dimensional continuation techniques are applied to study the bifurcation structure of a model of renal flow and pressure control. Integrating the main physiological mechanisms by which the individual nephron regulates the incoming blood flow, the model describes the interaction between...... the tubuloglomerular feedback and the response of the afferent arteriole. It is shown how a Hopf bifurcation leads the system to perform self-sustained oscillations if the feedback gain becomes sufficiently strong, and how a further increase of this parameter produces a folded structure of overlapping period...

Esophageal carcinoma treatment with self-expanding covered stent implanted in esophagus

International Nuclear Information System (INIS)

Liu Mingguo; Ji Yan; He Nengwei

2006-01-01

Objective: To investigate the clinical significance of the treatment to esophageal cancer by self- expanding covered stent implanted into esophagus. Methods: Under fluoroscopic guidance and with guidance wire , 20 self-expanding covered stents were implanted into stenotic part of esophagus to recanalize the esophagus, then follow up to observe the clinical symptom improved. Results: Technical success was obtained 20 cases without any complication. Clinical symptom were improved in shot time. Conclusions: self-expanding covered stent is implanted in stenotic part of esophageal carcinoma to treat esophageal stenosis and enable to improved clinical symptom in shot time, if combined with transcatheter arterial infusion and embolization, Radiotherapy, Chinese medical treatment, it enable to lengthen life time remarkably. (authors)

Adaptive Control of Electromagnetic Suspension System by HOPF Bifurcation

Directory of Open Access Journals (Sweden)

Aming Hao

2013-01-01

Full Text Available EMS-type maglev system is essentially nonlinear and unstable. It is complicated to design a stable controller for maglev system which is under large-scale disturbance and parameter variance. Theory analysis expresses that this phenomenon corresponds to a HOPF bifurcation in mathematical model. An adaptive control law which adjusts the PID control parameters is given in this paper according to HOPF bifurcation theory. Through identification of the levitated mass, the controller adjusts the feedback coefficient to make the system far from the HOPF bifurcation point and maintain the stability of the maglev system. Simulation result indicates that adjusting proportion gain parameter using this method can extend the state stability range of maglev system and avoid the self-excited vibration efficiently.

Transcatheter aortic-valve implantation with one single minimal contrast media injection.

Science.gov (United States)

Arrigo, Mattia; Maisano, Francesco; Haueis, Sabine; Binder, Ronald K; Taramasso, Maurizio; Nietlispach, Fabian

2015-06-01

Performing transcatheter aortic valve implantation (TAVI) with the use of minimal contrast in patients at high-risk for acute kidney injury (AKI). Contrast-induced nephropathy (CIN) is a major cause of AKI following TAVI and is associated with increased morbidity and mortality. The amount of contrast media used increases the risk for CIN. Computed tomography was omitted during the screening process. For the procedure transfemoral access was default. The self-expanding CoreValve prosthesis was chosen in all patients to minimize the risk of annular rupture in case of oversizing. Valve sizing was based on echocardiography, aortography, calcification on fluoroscopy, as well as weight and height of the patient. A single contrast injection was performed to confirm correct position of the pigtail catheter at the level of the annulus. The pigtail then served as the marker for the device landing zone. Intraprocedural assessment of the implantation result relied on echocardiography and hemodynamics. Five patients with severe aortic stenosis and at high risk for developing CIN were included. Device success was achieved in all patients and no major complications occurred. The median dose of injected contrast media was 8 ml (4-9). All but one patient had improved renal function after the intervention compared to baseline. Our study shows feasibility of performing TAVI with a single minimal contrast media injection, using a self-expandable valve. This technique has the potential to reduce the incidence of CIN. © 2015 Wiley Periodicals, Inc.

Esophagojejunal anastomotic leak managed with self expandable metallic stent

Directory of Open Access Journals (Sweden)

Arvind Madurandagam Annapillai

2013-01-01

Full Text Available Esophagealjejunal anastomotic leak after gastrectomy is a serious surgical emergency with high mortality. This report describes a 57-year-old male with esophagojejunal anastomotic leak following total gastrectomy for gastric cancer and was managed successfully with self-expandable metallic stent. To our knowledge this is the first such report from India. This case report highlights the need of interdisciplinary coordination in managing this difficult clinical situation. Endotherapy with self-expandable metallic stent (SEM provided twin benefits of improving respiratory embarrassment and the joy of eating. Therapy of such difficult cases must be individualized; however, and SEM stent usage is a viable option

Endovascular management of lap belt-related abdominal aortic injury in a 9-year-old child.

Science.gov (United States)

Papazoglou, Konstantinos O; Karkos, Christos D; Kalogirou, Thomas E; Giagtzidis, Ioakeim T

2015-02-01

Blunt abdominal aortic trauma is a rare occurrence in children with only a few patients having been reported in the literature. Most such cases have been described in the context of lap belt injuries. We report a 9-year-old boy who suffered lap belt trauma to the abdomen during a high-speed road traffic accident resulting to the well-recognized pattern of blunt abdominal injury, that is, the triad of intestinal perforation, fractures of the lumbar spine, and abdominal aortic injury. The latter presented with lower limb ischemia due to dissection of the infrarenal aorta and right common iliac artery. Revascularization was achieved by endovascular means using 2 self-expanding stents in the infrarenal aorta and the right common iliac artery. This case is one of the few reports of lap belt-related acute traumatic abdominal aortic dissection in a young child and highlights the feasibility of endovascular management in the pediatric population. Copyright © 2015 Elsevier Inc. All rights reserved.

Comparison of covered and uncovered self-expandable stents in the treatment of malignant biliary obstruction.

Science.gov (United States)

Flores Carmona, Diana Yamel; Alonso Lárraga, Juan Octavio; Hernández Guerrero, Angélica; Ramírez Solís, Mauro Eduardo

2016-05-01

Drainage with metallic stents is the treatment of choice in malignant obstructive jaundice. Technical and clinical success with metallic stents is obtained in over 90% and 80% of cases, respectively. There are self-expandable metallic stents designed to increase permeability. The aim of this study was to describe the results obtained with totally covered self-expandable and uncovered self-expandable metallic stents in the palliative treatment of malignant biliary obstruction. Sixty eight patients with malignant obstructive jaundice secondary to pancreatobiliary or metastatic disease not amenable to surgery were retrospectively included. Two groups were created: group A (covered self-expandable metallic stents) (n = 22) and group B (uncovered self-expandable metallic stents) (n = 46). Serum total bilirubin, direct bilirubin, alkaline phosphatase and gamma glutamyl transferase levels decreased in both groups and no statistically significant difference was detected (p = 0.800, p = 0.190, p = 0.743, p = 0.521). Migration was greater with covered stents but it was not statistically significant either (p = 0.101). Obstruction was greater in the group with uncovered stents but it was not statistically significant either (p = 0.476). There are no differences when using covered self-expandable stents or uncovered self-expandable stents in terms of technical and clinical success or complications in the palliative treatment of malignant obstructive jaundice.

Measurement of the aortic diameter in the asymptomatic Korean population: Assessment with multidetector CT

International Nuclear Information System (INIS)

Lee, Sang Hwan; Lee, Whal; Choi, Hyuck Jae; Kim, Dae Jin; Park, Eun Ah; Chung, Jin Wook; Park, Jae Hyung

2013-01-01

To determine normal reference values for aortic diameters in asymptomatic Korean adults. Three hundred adults without signs or symptoms of cardiovascular diseases were enrolled in this study. Aortic diameters were measured at nine predetermined levels on CT images. Aortic diameter measurements were adjusted for body surface area. Analysis of data was performed with regard to age, sex, weight, height and hypertension. Aortic diameters were 2.99 ± 0.57 cm at the ascending aorta, 2.54 ± 0.35 cm at the transverse aortic arch, 2.36 ± 0.35 cm at the proximal descending thoracic aorta (DTA), 2.23 ± 0.37 cm at the mid DTA, 2.17 ± 0.38 cm at the distal DTA, 2.16 ± 0.37 cm at the thoracoabdominal junction, 2.10, 00B1, 0.35 cm at the level of the celiac axis, 1.94, 00B1, 0.36 cm at the suprarenal aorta, 1.58 ± 0.24 cm at the aortic bifurcation. Men had slightly larger diameters than women (p < 0.05). All diameters increased with age and hypertension, with statistical significance (p < 0.01). And all aortic diameters increased with height (p < 0.05) except at the level of the aortic arch (p = 0.056), and increased with weight (p < 0.05) except at the level of the suprarenal aorta (p = 0.067). Male sex, higher weight and height, age and hypertension are associated with larger aortic diameters in asymptomatic Korean adults.

Contrast volume reduction using third generation dual source computed tomography for the evaluation of patients prior to transcatheter aortic valve implantation

Energy Technology Data Exchange (ETDEWEB)

Bittner, Daniel O. [University Hospital Erlangen, Friedrich-Alexander University Erlangen-Nuernberg (FAU), Department of Internal Medicine 2 (Cardiology), Erlangen (Germany); Harvard Medical School, Cardiac MR PET CT Program, Massachusetts General Hospital, Boston, MA (United States); Arnold, Martin; Klinghammer, Lutz; Schuhbaeck, Annika; Hell, Michaela M.; Muschiol, Gerd; Gauss, Soeren; Achenbach, Stephan; Marwan, Mohamed [University Hospital Erlangen, Friedrich-Alexander University Erlangen-Nuernberg (FAU), Department of Internal Medicine 2 (Cardiology), Erlangen (Germany); Lell, Michael; Uder, Michael [University Hospital Erlangen, Friedrich-Alexander University Erlangen-Nuernberg (FAU), Department of Radiology, Erlangen (Germany); Hoffmann, Udo [Harvard Medical School, Cardiac MR PET CT Program, Massachusetts General Hospital, Boston, MA (United States)

2016-12-15

Chronic renal failure is common in patients referred for transcatheter aortic valve implantation (TAVI). CT angiography is recommended and provides crucial information prior to TAVI. We evaluated the feasibility of a reduced contrast volume protocol for pre-procedural CT imaging. Forty consecutive patients were examined with prospectively ECG-triggered high-pitch spiral acquisition using a novel third-generation dual-source CT system; 38 ml contrast agent was used. Image quality was graded on a visual scale (1-4). Contrast attenuation was measured at the level of the aortic root and at the iliac bifurcation. Mean patient age was 82 ± 6 years (23 males; 58 %). Mean attenuation/average image quality was 285 ± 60 HU/1.5 at the aortic annulus compared to 289 ± 74 HU/1.8 at the iliac bifurcation (p = 0.77/p = 0.29). Mean estimated effective radiation dose was 2.9 ± 0.3 mSv. A repeat acquisition was necessary in one patient due to image quality. Out of the 35 patients who underwent TAVI, 31 (89 %) patients had no or mild aortic regurgitation. Thirty-two (91 %) patients were discharged successfully. Pre-procedural CTA with a total of 38 ml contrast volume is feasible and clinically useful, using third-generation dual-source CT, allowing comprehensive imaging for procedural success. (orig.)

Self-Expanding Metal Stenting for Palliation of Patients with Malignant Colonic Obstruction

DEFF Research Database (Denmark)

Meisner, Søren; González-Huix, Ferran; Vandervoort, Jo G

2012-01-01

Background. Self-expanding metal stents can alleviate malignant colonic obstruction in incurable patients and avoid palliative stoma surgery. Objective. Evaluate stent effectiveness and safety on palliation of patients with malignant colorectal strictures. Design. Two prospective, one Spanish....... Interventions(s). Self-expanding metal stent placement. Main Outcome Measures. Procedural success, clinical success, and safety. Results. Procedural success was 98.4% (251). Clinical success rates were 87.8% at 30 days, 89.7% at 3 months, 92.8% at 6 months, and 96% at 12 months. Overall perforation rate was 5...... for patients with malignant colonic obstruction should be self-expanding metal stent placement due to high rates of technical success and efficacy in symptom palliation and few complications....

Unusual presentation of aortic dissection: Post-coital acute paraplegia with renal failure

Directory of Open Access Journals (Sweden)

Dinith P Galabada

2014-01-01

Full Text Available We report the case of a 45-year-old chronic smoker who presented with acute paraplegia occurring during coitus and subsequently developed acute renal failure (ARF requiring dialysis. He had absent peripheral pulses in the lower limbs with evidence of acute ischemia. Doppler study showed dissecting aneurysm of thoracic aorta, thrombotic occlusion of the distal aorta from L1 level up to bifurcation and occlusion of the right renal artery by a thrombus that was confirmed by magnetic resonance imaging of the spine. He was not subjected to any vascular intervention as his lower limbs were not salvageable due to delay in the diagnosis. Post-coital aortic dissection and aortic dissection presenting with acute paraplegia and ARF are very rare. This is probably the first case report with post-coital acute aortic dissection presenting with paraplegia and ARF. This case emphasizes the importance of a careful examination of peripheral pulses in patients presenting with ARF and paraplegia.

Pancreatitis-Associated Splenic Artery Pseudoaneurysm: Endovascular Treatment with Self-Expandable Stent-Grafts

International Nuclear Information System (INIS)

Brountzos, Elias N.; Vagenas, Kostantinos; Apostolopoulou, Sotiria C.; Panagiotou, Irene; Lymberopoulou, Dimitra; Kelekis, Dimitrios A.

2003-01-01

We present a patient with a splenic arterypseudoaneurysm (SAPA) treated with placement of self-expandable stent-grafts. The procedure was complicated by stent-graft migration,but successful management resulted in lasting exclusion of the SAPA,while the patency of the splenic artery was preserved. This is the first report of self-expandable stent-graft treatment of SAPA

Treatment of Benign Tracheal Stenosis Utilizing Self-Expanding Nitinol Stents

International Nuclear Information System (INIS)

Sesterhenn, Andreas M.; Wagner, Hans-Joachim; Alfke, Heiko; Werner, Jochen A.; Lippert, Burkard M.

2004-01-01

We assessed the results of self-expanding metallic stent insertion into benign proximal tracheal stenosis in patients not appropriate or unfit for surgical repair. Proximal benign tracheal stenoses had occurred in 11 patients (7 men, 4 women, mean age 68.8 years) after long-time intubation (n = 6), tracheostomy (n = 4), or chondropathia (n = 1). Fourteen self-expanding nitinol stents were placed in the patients under general anesthesia with endoscopical and fluoroscopical guidance. Stent insertion was successful in all cases and led to immediate relief of the morphological and functional airway obstruction. No immediate complications were noted. During the mean follow-up period of 67.5 weeks we observed one recurrent dyspnea 3 months after implantation and granuloma formation at the stent insertion site in another patient. Both complications were successfully treated with additional stent insertion in one case and laser resection of granulomas in the other. Self-expanding nitinol stents should be considered for the treatment of benign proximal tracheal obstruction in selected patients for whom surgical repair is contraindicated

Renal Transplant Ureteral Stenosis: Treatment by Self-Expanding Metallic Stent

International Nuclear Information System (INIS)

Cantasdemir, Murat; Kantarci, Fatih; Numan, Furuzan; Mihmanli, Ismail; Kalender, Betul

2003-01-01

We report the use of a metallic stent in a transplant ureteral stenosis. A 28-year-old man with chronic renal failure due to chronic pyelonephritis, who received a living-donor renal transplant, presented with transplant ureteral stenosis. The stenosis was unresponsive to balloon dilation and was treated by antegrade placement of a self-expanding Memotherm stent. The stentedureter stayed patent for 3 years. It may be reasonable to treat post-transplant ureteral stenosis resistant to balloon dilation with self-expanding metallic stents. However, long-term follow-up is required to evaluate the efficacy of this treatment

Unfolding the Riddling Bifurcation

DEFF Research Database (Denmark)

Maistrenko, Yu.; Popovych, O.; Mosekilde, Erik

1999-01-01

We present analytical conditions for the riddling bifurcation in a system of two symmetrically coupled, identical, smooth one-dimensional maps to be soft or hard and describe a generic scenario for the transformations of the basin of attraction following a soft riddling bifurcation.......We present analytical conditions for the riddling bifurcation in a system of two symmetrically coupled, identical, smooth one-dimensional maps to be soft or hard and describe a generic scenario for the transformations of the basin of attraction following a soft riddling bifurcation....

Initial clinical experience with a sac-anchoring endoprosthesis for aortic aneurysm repair.

Science.gov (United States)

Donayre, Carlos E; Zarins, Christopher K; Krievins, Dainis K; Holden, Andrew; Hill, Andrew; Calderas, Carlos; Velez, Jaime; White, Rodney A

2011-03-01

All current aortic endografts depend on proximal and distal fixation to prevent migration. However, migration and rupture can occur, particularly in patients with aortic necks that are short or angulated, or both. We present our initial clinical experience with a new sac-anchoring endoprosthesis designed to anchor and seal the device within the aneurysm sac. The initial worldwide experience using a new endoprosthesis for the treatment of aortic aneurysms (Nellix Endovascular, Palo Alto, Calif) was reviewed. The endoprosthesis consists of dual balloon-expandable endoframes surrounded by polymer-filled endobags designed to obliterate the aneurysm sac and maintain endograft position. Clinical results and follow-up contrast computed tomography (CT) scans at 30 days and 6 and 12 months were reviewed. The endograft was successfully deployed in 21 patients with infrarenal aortic aneurysms measuring 5.7 ± 0.7 cm (range, 4.3-7.4 cm). Two patients with common iliac aneurysms were treated with sac-anchoring extenders that maintained patency of the internal iliac artery. Infusion of 71 ± 37 mL of polymer (range, 19-158 mL) into the aortic endobags resulted in complete aneurysm exclusion in all patients. Mean implant time was 76 ± 35 minutes, with 33 ± 17 minutes of fluoroscopy time and 180 ± 81 mL of contrast; estimated blood loss was 174 ± 116 mL. One patient died during the postoperative period (30-day mortality, 4.8%), and one died at 10 months from non-device-related causes. During a mean follow-up of 8.7 ± 3.1 months and a median of 6.3 months, there were no late aneurysm- or device-related adverse events and no secondary procedures. CT imaging studies at 6 months and 1 year revealed no increase in aneurysm size, no device migration, and no new endoleaks. One patient had a limited proximal type I endoleak at 30 days that resolved at 60 days and remained sealed. One patient has an ongoing distal type I endoleak near the iliac bifurcation, with no change in aneurysm

Expanding TAVI options: elective rotational atherectomy during trans-catheter aortic valve implantation

International Nuclear Information System (INIS)

Piccoli, Anna; Lunardi, Mattia; Ariotti, Sara; Ferrero, Valeria; Vassanelli, Corrado; Ribichini, Flavio

2015-01-01

Summary: Aortic valve stenosis (AVS) in the elderly is frequently associated to coronary artery disease (CAD). In patients with significant coronary stenosis surgical valve replacement is associated to coronary bypass grafting, but whether coronary angioplasty is needed in patients receiving trans-catheter aortic valve implantation (TAVI) is unknown. Given the frequent complexity of CAD in the elderly with calcific AVS, rotational atherectomy (RA) may be needed in some cases. No data are available about feasibility and safety of RA during TAVI. The need for myocardial revascularization in TAVI candidates is discussed, and a series of RA cases performed during TAVI is described

Expanding TAVI options: elective rotational atherectomy during trans-catheter aortic valve implantation

Energy Technology Data Exchange (ETDEWEB)

Piccoli, Anna; Lunardi, Mattia; Ariotti, Sara; Ferrero, Valeria; Vassanelli, Corrado; Ribichini, Flavio, E-mail: flavio.ribichini@univr.it

2015-01-15

Summary: Aortic valve stenosis (AVS) in the elderly is frequently associated to coronary artery disease (CAD). In patients with significant coronary stenosis surgical valve replacement is associated to coronary bypass grafting, but whether coronary angioplasty is needed in patients receiving trans-catheter aortic valve implantation (TAVI) is unknown. Given the frequent complexity of CAD in the elderly with calcific AVS, rotational atherectomy (RA) may be needed in some cases. No data are available about feasibility and safety of RA during TAVI. The need for myocardial revascularization in TAVI candidates is discussed, and a series of RA cases performed during TAVI is described.

Communication: Mode bifurcation of droplet motion under stationary laser irradiation

Energy Technology Data Exchange (ETDEWEB)

Takabatake, Fumi [Department of Physics, Graduate School of Science, Kyoto University, Kyoto 606-8502 (Japan); Department of Bioengineering and Robotics, Graduate School of Engineering, Tohoku University, Sendai, Miyagi 980-8579 (Japan); Yoshikawa, Kenichi [Faculty of Life and Medical Sciences, Doshisha University, Kyotanabe, Kyoto 610-0394 (Japan); Ichikawa, Masatoshi, E-mail: ichi@scphys.kyoto-u.ac.jp [Department of Physics, Graduate School of Science, Kyoto University, Kyoto 606-8502 (Japan)

2014-08-07

The self-propelled motion of a mm-sized oil droplet floating on water, induced by a local temperature gradient generated by CW laser irradiation is reported. The circular droplet exhibits two types of regular periodic motion, reciprocal and circular, around the laser spot under suitable laser power. With an increase in laser power, a mode bifurcation from rectilinear reciprocal motion to circular motion is caused. The essential aspects of this mode bifurcation are discussed in terms of spontaneous symmetry-breaking under temperature-induced interfacial instability, and are theoretically reproduced with simple coupled differential equations.

Five-Year Outcomes of the First Pivotal Clinical Trial of Balloon-Expandable Transcatheter Aortic Valve Replacement in Japan (PREVAIL JAPAN).

Science.gov (United States)

Sawa, Yoshiki; Takayama, Morimasa; Goto, Tsuyoshi; Takanashi, Shuichiro; Komiya, Tatsuhiko; Tobaru, Tetsuya; Maeda, Koichi; Kuratani, Toru; Sakata, Yasushi

2017-07-25

Transcatheter aortic valve replacement (TAVR) has been an alternative less invasive therapy for high-surgical risk/inoperable patients with aortic valve stenosis (AS) in Japan. We report 5-year outcomes of the first pivotal clinical trial of TAVR in Japan (PREVAIL JAPAN).Methods and Results:A total of 64 patients with AS who were considered unsuitable candidates for surgery were enrolled at 3 centers in Japan (mean age: 84.3±6.1 years, female: 65.6%, STS score: 9.0±4.5%). Transfemoral approach (TF) and transapical approach (TA) was performed in 37 patients and 27 patients, respectively. At 5 years, freedom from all-cause death was 52.7% (TF: 51.3%, TA: 56.3%). Risk of all stroke at 5-year was 15.8% (TF: 8.9%, TA: 25.5%) and risk of major adverse cardiac and cerebrovascular events at 5 years was 58.0% (TF: 51.3%, TA: 69.2%). Mild or greater aortic regurgitation (AR) at 1 week was not associated with increased all-cause death at 5 years (69.1%) compared with none or trace AR (48.3%) (P=0.184). Patients with high STS score (>8) had higher mortality rate than those with low STS scores (≤8). The 5-year data from PREVAIL JAPAN show the clinical benefit of TAVR and suggest that balloon-expandable TAVR is an effective treatment option for Japanese patients with severe AS who are not suitable for surgery. (Funded by Edwards Lifesciences Limited; ClinicalTrials.gov number, NCT01113983.).

Safety of endoscopic removal of self-expandable stents after treatment of benign esophageal diseases

NARCIS (Netherlands)

van Halsema, Emo E.; Wong Kee Song, Louis M.; Baron, Todd H.; Siersema, Peter D.; Vleggaar, Frank P.; Ginsberg, Gregory G.; Shah, Pari M.; Fleischer, David E.; Ratuapli, Shiva K.; Fockens, Paul; Dijkgraaf, Marcel G. W.; Rando, Giacomo; Repici, Alessandro; van Hooft, Jeanin E.

2013-01-01

Temporary placement of self-expandable stents has been increasingly used for the management of benign esophageal diseases. To evaluate the safety of endoscopic removal of esophageal self-expandable stents placed for the treatment of benign esophageal diseases. Multicenter retrospective study. Six

Familial Thoracic Aortic Aneurysm with Dissection Presenting as Flash Pulmonary Edema in a 26-Year-Old Man

Directory of Open Access Journals (Sweden)

Sabry Omar

2014-01-01

Full Text Available We are reporting a case of familial thoracic aortic aneurysm and dissection in a 26-year-old man with no significant past medical history and a family history of dissecting aortic aneurysm in his mother at the age of 40. The patient presented with cough, shortness of breath, and chest pain. Chest X-ray showed bilateral pulmonary infiltrates. CT scan of the chest showed a dissection of the ascending aorta. The patient underwent aortic dissection repair and three months later he returned to our hospital with new complaints of back pain. CT angiography showed a new aortic dissection extending from the left carotid artery through the bifurcation and into the iliac arteries. The patient underwent replacement of the aortic root, ascending aorta, total aortic arch, and aortic valve. The patient recovered well postoperatively. Genetic studies of the patient and his children revealed no mutations in ACTA2, TGFBR1, TGFBR2, TGFB2, MYH11, MYLK, SMAD3, or FBN1. This case report focuses on a patient with familial TAAD and discusses the associated genetic loci and available screening methods. It is important to recognize potential cases of familial TAAD and understand the available screening methods since early diagnosis allows appropriate management of risk factors and treatment when necessary.

Second Generation Self-Inflating Tissue Expanders: A Two-Year Experience

Directory of Open Access Journals (Sweden)

Jamal Omran Al Madani

2014-01-01

Full Text Available Background. Tissue expansion is a well-established surgical technique that produces an additional amount of normal skin to cover a defect. This technique is appealing because the skin quality and color are from the patient’s own. The widely used injectable expanders are of great reliability but carry the disadvantage of being painful during injection and most of the time require multiple clinic visits. So the idea of self-inflation became attractive and hydrogel expanders were developed and became widely known for being painless during clinic visit and decrease number of visits. The first generation expanders were modified by adding an enclosing plastic shell to decrease the unopposed expansion that occurred in the first generation expanders, which lead to pressure necrosis of the skin flaps. This made it an attractive option for tissue expansion in children and some adult patients. Patients, Materials, and Methods. Charts of 17 patients were retrospectively reviewed, all of them had second generation self-inflating expanders implanted over a 2-year period for one of two purposes, the treatment of giant nevi or burn scars. Results. Fifteen patients were females and 2 were males. The indication was large burn scar in 14 cases (14/17, in which 47/55 expanders were implanted, and giant nevus in 3/17 cases in which 8/55 expanders were implanted. Extrusion of the expander occurred in 8/55 expanders (14.5%, which occurred in 6/14 patients. The highest percentage of extrusion occurred in the neck in which two out of three expanders extruded; otherwise this complication does not seem to be related to the indication, gender, nor age of the patients. It seems to be that it is technical in nature. The patients did not have to get any injections to fill the tissue expanders, which made the expansion process less painful and more convenient. Conclusion. This seems to be currently the largest published review in which second generation expanders were used

Bifurcations sights, sounds, and mathematics

CERN Document Server

Matsumoto, Takashi; Kokubu, Hiroshi; Tokunaga, Ryuji

1993-01-01

Bifurcation originally meant "splitting into two parts. " Namely, a system under­ goes a bifurcation when there is a qualitative change in the behavior of the sys­ tem. Bifurcation in the context of dynamical systems, where the time evolution of systems are involved, has been the subject of research for many scientists and engineers for the past hundred years simply because bifurcations are interesting. A very good way of understanding bifurcations would be to see them first and study theories second. Another way would be to first comprehend the basic concepts and theories and then see what they look like. In any event, it is best to both observe experiments and understand the theories of bifurcations. This book attempts to provide a general audience with both avenues toward understanding bifurcations. Specifically, (1) A variety of concrete experimental results obtained from electronic circuits are given in Chapter 1. All the circuits are very simple, which is crucial in any experiment. The circuits, howev...

Self-Expandable Metallic Stent Placement for the Palliation of Esophageal Cancer.

Science.gov (United States)

Kim, Kun Yung; Tsauo, Jiaywei; Song, Ho Young; Kim, Pyeong Hwa; Park, Jung Hoon

2017-07-01

Esophageal stents have been used to palliate patients with dysphagia caused by esophageal cancer. Early rigid plastic prostheses have been associated with a high risk of complications. However, with the development of self-expanding stents, it has developed into a widely accepted method for treating malignant esophageal strictures and esophagorespiratory fistulas (ERFs). The present review covers various aspects of self-expanding metallic stent placement for palliating esophageal cancer, including its types, placement procedures, indications, contraindications, complications, and some of innovations that will become available in the future. © 2017 The Korean Academy of Medical Sciences.

Quantitative angiography methods for bifurcation lesions

DEFF Research Database (Denmark)

Collet, Carlos; Onuma, Yoshinobu; Cavalcante, Rafael

2017-01-01

Bifurcation lesions represent one of the most challenging lesion subsets in interventional cardiology. The European Bifurcation Club (EBC) is an academic consortium whose goal has been to assess and recommend the appropriate strategies to manage bifurcation lesions. The quantitative coronary...... angiography (QCA) methods for the evaluation of bifurcation lesions have been subject to extensive research. Single-vessel QCA has been shown to be inaccurate for the assessment of bifurcation lesion dimensions. For this reason, dedicated bifurcation software has been developed and validated. These software...

Detection of bifurcations in noisy coupled systems from multiple time series

International Nuclear Information System (INIS)

Williamson, Mark S.; Lenton, Timothy M.

2015-01-01

We generalize a method of detecting an approaching bifurcation in a time series of a noisy system from the special case of one dynamical variable to multiple dynamical variables. For a system described by a stochastic differential equation consisting of an autonomous deterministic part with one dynamical variable and an additive white noise term, small perturbations away from the system's fixed point will decay slower the closer the system is to a bifurcation. This phenomenon is known as critical slowing down and all such systems exhibit this decay-type behaviour. However, when the deterministic part has multiple coupled dynamical variables, the possible dynamics can be much richer, exhibiting oscillatory and chaotic behaviour. In our generalization to the multi-variable case, we find additional indicators to decay rate, such as frequency of oscillation. In the case of approaching a homoclinic bifurcation, there is no change in decay rate but there is a decrease in frequency of oscillations. The expanded method therefore adds extra tools to help detect and classify approaching bifurcations given multiple time series, where the underlying dynamics are not fully known. Our generalisation also allows bifurcation detection to be applied spatially if one treats each spatial location as a new dynamical variable. One may then determine the unstable spatial mode(s). This is also something that has not been possible with the single variable method. The method is applicable to any set of time series regardless of its origin, but may be particularly useful when anticipating abrupt changes in the multi-dimensional climate system

Detection of bifurcations in noisy coupled systems from multiple time series

Science.gov (United States)

Williamson, Mark S.; Lenton, Timothy M.

2015-03-01

We generalize a method of detecting an approaching bifurcation in a time series of a noisy system from the special case of one dynamical variable to multiple dynamical variables. For a system described by a stochastic differential equation consisting of an autonomous deterministic part with one dynamical variable and an additive white noise term, small perturbations away from the system's fixed point will decay slower the closer the system is to a bifurcation. This phenomenon is known as critical slowing down and all such systems exhibit this decay-type behaviour. However, when the deterministic part has multiple coupled dynamical variables, the possible dynamics can be much richer, exhibiting oscillatory and chaotic behaviour. In our generalization to the multi-variable case, we find additional indicators to decay rate, such as frequency of oscillation. In the case of approaching a homoclinic bifurcation, there is no change in decay rate but there is a decrease in frequency of oscillations. The expanded method therefore adds extra tools to help detect and classify approaching bifurcations given multiple time series, where the underlying dynamics are not fully known. Our generalisation also allows bifurcation detection to be applied spatially if one treats each spatial location as a new dynamical variable. One may then determine the unstable spatial mode(s). This is also something that has not been possible with the single variable method. The method is applicable to any set of time series regardless of its origin, but may be particularly useful when anticipating abrupt changes in the multi-dimensional climate system.

Detection of bifurcations in noisy coupled systems from multiple time series

Energy Technology Data Exchange (ETDEWEB)

Williamson, Mark S., E-mail: m.s.williamson@exeter.ac.uk; Lenton, Timothy M. [Earth System Science Group, College of Life and Environmental Sciences, University of Exeter, Laver Building, North Park Road, Exeter EX4 4QE (United Kingdom)

2015-03-15

We generalize a method of detecting an approaching bifurcation in a time series of a noisy system from the special case of one dynamical variable to multiple dynamical variables. For a system described by a stochastic differential equation consisting of an autonomous deterministic part with one dynamical variable and an additive white noise term, small perturbations away from the system's fixed point will decay slower the closer the system is to a bifurcation. This phenomenon is known as critical slowing down and all such systems exhibit this decay-type behaviour. However, when the deterministic part has multiple coupled dynamical variables, the possible dynamics can be much richer, exhibiting oscillatory and chaotic behaviour. In our generalization to the multi-variable case, we find additional indicators to decay rate, such as frequency of oscillation. In the case of approaching a homoclinic bifurcation, there is no change in decay rate but there is a decrease in frequency of oscillations. The expanded method therefore adds extra tools to help detect and classify approaching bifurcations given multiple time series, where the underlying dynamics are not fully known. Our generalisation also allows bifurcation detection to be applied spatially if one treats each spatial location as a new dynamical variable. One may then determine the unstable spatial mode(s). This is also something that has not been possible with the single variable method. The method is applicable to any set of time series regardless of its origin, but may be particularly useful when anticipating abrupt changes in the multi-dimensional climate system.

The technique study and primary clinical application of inverted Y-shaped self-expandable metal airway stent

International Nuclear Information System (INIS)

Han Xinwei; Wu Gang; Ma Ji; Yang Ruimin; Guan Sheng; Ma Nan; Wang Yanli

2007-01-01

Objective: To investigate the feasibility and primary therapeutic effect of inverted Y-shaped self-expandable metal stent for complex airway stenosis. Methods: On the standpoint of the peculiar anatomic structure and the pathological changes of complex airway stenosis, we designed the inverted Y-shaped self-expandable metal stent. Under the fluoroscopic guidance, 7 stents were implanted in 7 cases of airway complex stenosis. Results: The inverted Y-shaped self-expandable metal stents were placed seccussfully, with instantaneous relief of dyspnea and improvement of living quality. Conclusion: The placement of inverted Y-shaped self-expandable metal stent is feasible and safe for treating airway complex stenosis. (authors)

Patients' self-reported function, symptoms and health-related quality of life before and 6 months after transcatheter aortic valve implantation and surgical aortic valve replacement.

Science.gov (United States)

Olsson, Karin; Nilsson, Johan; Hörnsten, Åsa; Näslund, Ulf

2017-03-01

Aortic stenosis is the most common valve disease in western countries and has poor prognosis without treatment. Surgical aortic valve replacement (SAVR) is the gold standard, and transcatheter aortic valve implantation (TAVI) is a new method that is used in high-risk patients who are denied surgery. The purpose of treatment is not only to save life, but also to reduce symptoms and increase health-related quality of life (HRQoL). The aim of this study was to describe patients' self-reported outcomes in terms of physical function, symptoms, dependence, HRQoL, and cognitive function after TAVI and SAVR. All patients treated with TAVI during 1 year ( n = 24) and age-matched patients treated with SAVR ( n = 24) were included. Data were collected on the day before and at 6 months after treatment using structural questionnaires. Self-rated function was low before treatment and increased at follow-up. A quarter of all patients reported syncope at baseline, and none reported this at follow-up. Breathlessness was reported by all patients to be the most limiting cardiac symptom, but the TAVI patients reported more severe symptoms. At 6 months' follow-up, symptoms were reduced, but breathlessness and fatigue were still common, especially in the TAVI group. HRQoL, which was very low in the TAVI group at baseline, increased in all dimensions except social function. We found no change in cognitive function or dependence at follow-up. There was no difference in the size of improvement between groups. The results could be helpful when informing future patients in order to give them realistic expectations.

The treatment of complex airway diseases with inverted Y-shaped self-expandable metal stent

International Nuclear Information System (INIS)

Li Jianming; Jia Guangzhi

2011-01-01

Objective: To investigate the application and therapeutic effects of inverted Y-shaped self-expandable metal airway stent in treating complex airway diseases (stenosis or fistula). Methods: According to the distinctive anatomic structure and the pathological changes of complex airway stenosis or fistula, the inverted y-shaped self-expandable metal airway stent was designed. Under fluoroscopic monitoring, a total of 12 inverted Y-shaped self-expandable metal stents were implanted in 12 patients with complex airway diseases. Results: Stent placement in the trachea-bronchial tree was technically successful in all patients. After the operation, the symptom of dyspnea was immediately relieved and the bucking following food intake disappeared. The general physical condition and living quality were much improved in all patients. Conclusion: The use of inverted Y-shaped self-expandable metal airway stent for the management of complex airway stenosis involving the tracheal carina was a simple and safe procedure and it has satisfactory short-term clinical results. (authors)

Simple or Complex Stenting for Bifurcation Coronary Lesions: A Patient-Level Pooled-Analysis of the Nordic Bifurcation Study and the British Bifurcation Coronary Study

DEFF Research Database (Denmark)

Behan, Miles W; Holm, Niels Ramsing; Curzen, Nicholas P

2011-01-01

Background— Controversy persists regarding the correct strategy for bifurcation lesions. Therefore, we combined the patient-level data from 2 large trials with similar methodology: the NORDIC Bifurcation Study (NORDIC I) and the British Bifurcation Coronary Study (BBC ONE). Methods and Results— B...

Differences in Endothelial Injury After Balloon Angioplasty, Insertion of Balloon-Expanded Stents or Release of Self-Expanding Stents: An Electron Microscopic Experimental Study

International Nuclear Information System (INIS)

Harnek, Jan; Zoucas, Evita; Carlemalm, Erik; Cwikiel, Wojciech

1999-01-01

Purpose: To evaluate which of six different commonly available stents inserted into an artery without percutaneous transluminal angioplasty (PTA) causes the least endothelial damage. To compare the degree of endothelial injury after insertion of such a stent with injury caused by PTA. Methods: Twelve healthy pigs were used in the experiments. In the first part of the study six different types of stents were inserted into the common iliac arteries. In the second part of the study self-expanding stents with large spaces between the wires were used. PTA was performed in the contralateral iliac artery. The pigs were killed immediately after the procedure and resected specimens examined after fixation, using scanning electron microscopy. Results: All procedures but two were accomplished successfully. More endothelium was preserved after insertion of self-expanding stents with large spaces between the wires, compared with stents with small spaces and balloon-expanded stents. After insertion of self-expanding stents with large spaces, 50.1% ± 16.4% of the endothelium remained intact, compared with only 5.6% ± 7.7% after PTA. The difference was statistically significant (p < 0.001). Conclusion: Self-expanding stents with large spaces between the wires, inserted without PTA, cause less damage to the endothelium than other stents and significantly less damage than PTA

Treatment of tracheobronchial stenosis with a self-expandable metallic stents

Energy Technology Data Exchange (ETDEWEB)

Kim, Yong Soo; Jeon, Seok Chol; Choi, Chul Seung; Choi, Yo Won; Hahm, Chang Kok [College of Medicine, Hanyang University, Seoul (Korea, Republic of)

1994-07-15

We analysed the role of modified Gianturco self-expandable stents in the treatment of tracheobronchial stenosis in 13 patients. We inserted modified Gianturco self-expandable stents under the fluoroscopic and bronchoscopic guidance. There were stenosis in the trachea(n=2), the right main bronchus(n=2), and the left main bronchus(n=9). The causes of the stenosis were endobronchial tuberculosis(n=10), intubation granuloma(n=1), restenosis after surgical reconstruction(n=2). Dyspnea or wheezing was improved within 1 or 2 days following the procedure. There were 32% and 22% respective increase in average FEV1 and FVC. Lung perfusion scan showed 9.6% increase of perfusion in the involved lung. No complications related to the procedure were encountered. During follow-up period of up to 31 months, 2 patients showed tracheal or bronchial restenosis, at 3 and 6 months, retrospectively. There was a distal migration of the stents in one case. During the follow up period after stent insertion, improvement of the obstructive changes and dyspnea persisted in 10 out of 13 patients. The modified Gianturco self-expandable metallic stents may be a good choice for the treatment of tracheobronchial stenosis, either as a primary treatment, or when the reconstruction failed.

Long-term outcome of self expandable metal stents for biliary obstruction in chronic pancreatitis.

Science.gov (United States)

Waldthaler, Alexander; Schütte, Kerstin; Weigt, Jochen; Kropf, Siegfried; Malfertheiner, Peter; Kahl, Stefan

2013-01-10

Insertion of a self-expandable metal stent is still controversial for treatment of benign common bile duct stenosis but can be a valuable alternative to surgical treatment. Aim of our study was to analyze the efficacy of covered and uncovered self-expandable metal stent in patients with chronic pancreatitis and common bile duct stenosis. Twenty patients with common bile duct stenosis due to alcoholic chronic pancreatitis were retrospective analyzed. All patients had advanced chronic pancreatitis, presenting with calcifications in pancreatic head. Uncovered self-expandable metal stent (uSEMS) were used in 11 patients (3 females, 8 males) while in 9 patients (3 females, 6 males) partially covered self-expandable metal stent (cSEMS) were inserted. All patients treated with self-expandable metal stent had contraindications for surgery. Overall mean follow up time was 155 weeks: 206 (52-412) weeks in uSEMS, and 93 (25-233) weeks in cSEMS, respectively. Stent patency was in mean 118 weeks: 159 (44-412) weeks in uSEMS and 67 (25-150) weeks in cSEMS (P=0.019). In the uSEMS group, reintervention was necessary in 5 patients (45%) due to stent obstruction, whereas in the cSEMS group 4 patients (44%) needed reintervention (2 obstructions, 2 migration). Stent migration is an early complication, compared to obstruction (P<0.05), and in cSEMS obstruction occurred significantly earlier compared to uSEMS (P<0.05). Patency of uSEMS was significantly longer compared to partially cSEMS. Available self-expandable metal stent, unfortunately, do not meet the demands on successful treatment of benign common bile duct stenosis.

Safety of endoscopic removal of self-expandable stents after treatment of benign esophageal diseases.

Science.gov (United States)

van Halsema, Emo E; Wong Kee Song, Louis M; Baron, Todd H; Siersema, Peter D; Vleggaar, Frank P; Ginsberg, Gregory G; Shah, Pari M; Fleischer, David E; Ratuapli, Shiva K; Fockens, Paul; Dijkgraaf, Marcel G W; Rando, Giacomo; Repici, Alessandro; van Hooft, Jeanin E

2013-01-01

Temporary placement of self-expandable stents has been increasingly used for the management of benign esophageal diseases. To evaluate the safety of endoscopic removal of esophageal self-expandable stents placed for the treatment of benign esophageal diseases. Multicenter retrospective study. Six tertiary care centers in the United States and Europe. A total of 214 patients with benign esophageal diseases undergoing endoscopic stent removal. Endoscopic stent removal. Endoscopic techniques for stent removal, time to stent removal, and adverse events related to stent removal. A total of 214 patients underwent a total of 329 stent extractions. Stents were mainly placed for refractory strictures (49.2%) and fistulae (49.8%). Of the removed stents, 52% were fully covered self-expandable metal stents (FCSEMSs), 28.6% were partially covered self-expandable metal stents (PCSEMSs), and 19.5% were self-expandable plastic stents. A total of 35 (10.6%) procedure-related adverse events were reported, including 7 (2.1%) major adverse events. Multivariate analysis revealed that use of PCSEMSs (P stent removal. Favorable factors for successful stent removal were FCSEMSs (P ≤ .012) and stent migration (P = .010). No significant associations were found for stent indwelling time (P = .145) and stent embedding (P = .194). Retrospective analysis, only tertiary care centers. With an acceptable major adverse event rate of 2.1%, esophageal stent removal in the setting of benign disease was found to be a safe and feasible procedure. FCSEMSs were more successfully removed than self-expandable plastic stents and PCSEMSs. Adverse events caused by stent removal were not time dependent. Copyright © 2013 American Society for Gastrointestinal Endoscopy. Published by Mosby, Inc. All rights reserved.

Morphometric analysis of torso arterial anatomy with implications for resuscitative aortic occlusion.

Science.gov (United States)

Stannard, Adam; Morrison, Jonathan J; Sharon, Danny J; Eliason, Jonathan L; Rasmussen, Todd E

2013-08-01

Hemorrhage is a leading cause of death in military and civilian trauma. Despite the importance of the aorta as a site of hemorrhage control and resuscitative occlusion, detailed knowledge of its morphometry is lacking. The objective of this study was to characterize aortic morphometry in a trauma population, including quantification of distances as well as and diameters and definition of relevant aortic zones. Center line measures were made (Volume Viewer) from contrast computed tomography (CT) scans of male trauma patients (18-45 years). Aortic zones were defined based on branch arteries. Zone I includes left subclavian to celiac; Zone II includes celiac to caudal renal; Zone III includes caudal renal to aortic bifurcation. Zone lengths were calculated and correlated to a novel external measure of torso extent (symphysis pubis to sternal notch). Eighty-eight males (mean [SD], 28 [4] years) had CT scans for the study. The median (interquartile range) lengths (mm) of Zones I, II, and III were 210 mm (202-223 mm), 33 mm (28-38 mm), and 97 mm (91-103 mm), respectively. Median aortic diameters at the left subclavian, celiac, and lowest renal arteries were 21 mm (20-23 mm), 18 mm (16-19 mm), and 15 mm (14-16 mm), respectively, and the terminal aortic diameter was 14 mm (13-15 mm). The correlation of determination for descending aortic length (all zones) against torso extend was r = 0.454. This study provides a morphometric analysis of the aorta in a male population, demonstrating consistency of length and diameter while defining distinct axial zones. Findings suggest that center line aortic distances correlate with a simple, external measure of torso extent. Morphometric study of the aorta using CT data may facilitate the development and implementation of occlusion techniques to manage noncompressible torso, pelvic, and junctional femoral hemorrhage.

Endovascular therapy of carotid stenosis with self-expandable stent

International Nuclear Information System (INIS)

Liu Jianmin; Huang Qinghai; Hong Bo; Xu Yi; Zhao Wenyuan; Zhang Yongwei; Zhang Long; Zhou Xiaoping

2002-01-01

Objective: To summarize the experience of endovascular treatment of carotid stenosis with expandable stents. Methods: Fifty-two patients with carotid stenosis who experienced repeated transient ischemic attacks or cerebral infarction were admitted to our hospital. The stenosis was pre-expanded with undetachable balloon, and self-expandable stents were implanted across the stenosis. A balloon catheter was used to further expand stents in 29 patients. Results: The stent was accurately implanted, and total disappearance of stenosis was obtained in 34 patients, the degree of stenosis reduced more than 90% in 16 patients, and more than 70% in 2 patients. The patients recovered well and no complications related to the procedure occurred. None experienced TIA or infarction postoperatively in 52 cases and follow-up imaging in 19 patients (6 - 12 months) demonstrated no restenosis. Conclusion: Endovascular stenting may be a safe and valid choice for the treatment of extracranial carotid stenosis

Plasma levels of plasmin-antiplasmin-complexes are predictive for small abdominal aortic aneurysms expanding to operation-recommendable sizes

DEFF Research Database (Denmark)

Lindholt, Jes Sanddal; Jørgensen, B; Fasting, H

2001-01-01

Three proteolytic systems seem involved in the aneurysmal degradation of the aortic wall. Plasmin is a common activator of the systems and could thus be predictive for the progression of abdominal aortic aneurysms (AAAs).......Three proteolytic systems seem involved in the aneurysmal degradation of the aortic wall. Plasmin is a common activator of the systems and could thus be predictive for the progression of abdominal aortic aneurysms (AAAs)....

Bifurcation structure of parameter plane for a family of unimodal piecewise smooth maps: Border-collision bifurcation curves

International Nuclear Information System (INIS)

Sushko, Iryna; Agliari, Anna; Gardini, Laura

2006-01-01

We study the structure of the 2D bifurcation diagram for a two-parameter family of piecewise smooth unimodal maps f with one break point. Analysing the parameters of the normal form for the border-collision bifurcation of an attracting n-cycle of the map f, we describe the possible kinds of dynamics associated with such a bifurcation. Emergence and role of border-collision bifurcation curves in the 2D bifurcation plane are studied. Particular attention is paid also to the curves of homoclinic bifurcations giving rise to the band merging of pieces of cyclic chaotic intervals

Relative Lyapunov Center Bifurcations

DEFF Research Database (Denmark)

Wulff, Claudia; Schilder, Frank

2014-01-01

Relative equilibria (REs) and relative periodic orbits (RPOs) are ubiquitous in symmetric Hamiltonian systems and occur, for example, in celestial mechanics, molecular dynamics, and rigid body motion. REs are equilibria, and RPOs are periodic orbits of the symmetry reduced system. Relative Lyapunov...... center bifurcations are bifurcations of RPOs from REs corresponding to Lyapunov center bifurcations of the symmetry reduced dynamics. In this paper we first prove a relative Lyapunov center theorem by combining recent results on the persistence of RPOs in Hamiltonian systems with a symmetric Lyapunov...... center theorem of Montaldi, Roberts, and Stewart. We then develop numerical methods for the detection of relative Lyapunov center bifurcations along branches of RPOs and for their computation. We apply our methods to Lagrangian REs of the N-body problem....

Bifurcation structure and stability in models of opposite-signed vortex pairs

International Nuclear Information System (INIS)

Luzzatto-Fegiz, Paolo

2014-01-01

We employ a recently developed numerical method to examine in detail the properties of opposite-signed, translating vortex pairs. We first consider a uniform-vortex approximation; for this flow, previous studies have found essential differences between rotating and translating configurations, and have encountered numerical difficulties at the boundary between the two types of equilibria. Recently, Luzzatto-Fegiz and Williamson (2012 J. Fluid Mech. 706 323–50) used an imperfect velocity-impulse (IVI) diagram to show that the rotating pairs have a translating counterpart, arising from a bifurcation of the classical translating configurations. In this paper, we expand this IVI diagram to find two new branches of steady vortices, including antisymmetric pairs, as well as vortices without any symmetry. We next consider more realistic models for flows at moderate Reynolds number Re, by computing solution families based on a discretized Chaplygin–Lamb dipole. We find that, as the accuracy of the discretization improves, the bifurcated branches shrink rapidly, while the unstable portion of the basic solution family becomes smaller. These results indicate that the bifurcation structure of moderate-Re flows can be very different from that of solutions that use a single patch per vortex. (papers)

Bifurcation structure and stability in models of opposite-signed vortex pairs

Energy Technology Data Exchange (ETDEWEB)

Luzzatto-Fegiz, Paolo, E-mail: Paolo.Luzzatto-Fegiz@damtp.cam.ac.uk [Churchill College, Cambridge CB3 0DS (United Kingdom)

2014-06-01

We employ a recently developed numerical method to examine in detail the properties of opposite-signed, translating vortex pairs. We first consider a uniform-vortex approximation; for this flow, previous studies have found essential differences between rotating and translating configurations, and have encountered numerical difficulties at the boundary between the two types of equilibria. Recently, Luzzatto-Fegiz and Williamson (2012 J. Fluid Mech. 706 323–50) used an imperfect velocity-impulse (IVI) diagram to show that the rotating pairs have a translating counterpart, arising from a bifurcation of the classical translating configurations. In this paper, we expand this IVI diagram to find two new branches of steady vortices, including antisymmetric pairs, as well as vortices without any symmetry. We next consider more realistic models for flows at moderate Reynolds number Re, by computing solution families based on a discretized Chaplygin–Lamb dipole. We find that, as the accuracy of the discretization improves, the bifurcated branches shrink rapidly, while the unstable portion of the basic solution family becomes smaller. These results indicate that the bifurcation structure of moderate-Re flows can be very different from that of solutions that use a single patch per vortex. (papers)

Feasibility of using bulk metallic glass for self-expandable stent applications.

Science.gov (United States)

Praveen Kumar, Gideon; Jafary-Zadeh, Mehdi; Tavakoli, Rouhollah; Cui, Fangsen

2017-10-01

Self-expandable stents are widely used to restore blood flow in a diseased artery segment by keeping the artery open after angioplasty. Despite the prevalent use of conventional crystalline metallic alloys, for example, nitinol, to construct self-expandable stents, new biomaterials such as bulk metallic glasses (BMGs) are being actively pursued to improve stent performance. Here, we conducted a series of analyses including finite element analysis and molecular dynamics simulations to investigate the feasibility of using a prototypical Zr-based BMG for self-expandable stent applications. We model stent crimping of several designs for different percutaneous applications. Our results indicate that BMG-based stents with diamond-shaped crowns suffer from severe localization of plastic deformation and abrupt failure during crimping. As a possible solution, we further illustrate that such abrupt failure could be avoided in BMG-based stents without diamond shape crowns. This work would open a new horizon for a quest toward exploiting superior mechanical and functional properties of metallic glasses to design future stents. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1874-1882, 2017. © 2016 Wiley Periodicals, Inc.

Percutaneous endovascular stent-graft treatment of aortic aneurysms and dissections: new techniques and initial experience

Energy Technology Data Exchange (ETDEWEB)

Lee, Do Yun; Choi, Dong Hoon; Kang, Sung Gwon; Lee, Kwang Hoon; Won, Jong Yun [Yonsei University College of Medicine, Seoul (Korea, Republic of); Kang, Sung Gwon [Chosun University College of Medicine, Gwangju (Korea, Republic of); Won, Je Whan [Aju University College of Medicine, Suwon (Korea, Republic of); Song, Ho Young [Ulsan University College of Medicine, Seoul (Korea, Republic of)

2003-01-01

To evaluate the feasibility, safety and effectiveness of a newly designed percutaneously implanted separate stent-graft (SSG) for the treatment of aortic aneurysms and dissections. Using a percutaneous technique, SSG placement (in the descending thoracic aorta in 26 cases and infrarenal abdominal aorta in 24) was attempted in 50 patients with aortic aneurysms (n=27) or dissection (n=23). All SSGs were individually constructed using self-expandable nitinol stents and a Dacron graft, and were introduced through a 12 F sheath and expanded to a diameter of 20-34 mm. In all cases, vascular access was through the femoral artery. The clinical status of each patient was monitored, and postoperative CT was performed within one week of the procedure and at 3-6 month intervals afterwards. Endovascular stent-graft deployment was technically successful in 49 of 50 patients (98%). The one failure was due to torsion of the unsupported graft during deployment. Successful exclusion of aneurysms and the primary entry tears of dissections was achieved in all but three patients with aortic dissection. All patients in whom technical success was achieved showed complete thrombosis of the thoracic false lumen or aneurysmal sac, and the overall technique success rate was 92%. In addition, sixteen patients demonstrated complete resolution of the dissected thoracic false lumen (n=9) or aneurysmal sac (n=7). Immediate post-operative complications occurred at the femoral puncture site in one patient with an arteriovenous fistula, and in two, a new saccular aneurysm developed at the distal margin of the stent. No patients died, and there was no instance of paraplegia, stroke, side-branch occlusion or infection during the subsequent mean follow-up period of 9.4 (range, 2 to 26) months. In patients with aortic aneurysm and dissection, treatment with a separate percutaneously inserted stent-graft is technically feasible, safe, and effective.

Sequential Hybrid Repair of Aorta and Bilateral Common Iliac Arteries Secondary to Chronic Aortic Dissection with Extensive Aneurysmal Degeneration in a Marfan Patient.

Science.gov (United States)

Hinojosa, Carlos A; Anaya-Ayala, Javier E; Laparra-Escareno, Hugo; Lizola, Rene; Torres-Machorro, Adriana

2017-09-01

Marfan syndrome is a connective tissue disorder associated with aortic dissection, aneurysmal degeneration and rupture. These cardiovascular complications represent the main cause of mortality, therefore repair is indicated. We present a 35-year-old woman who experienced acute onset of chest pain. Her imaging revealed a chronic DeBakey type I dissection with aortic root dilation and descending thoracic aneurysmal degeneration. She underwent a Bentall procedure and endovascular exclusion of the descending thoracic aortic aneurysm. She was closely followed and 2 years later a computed tomography angiography (CTA) revealed the aneurysmal degeneration of the thoracoabominal aorta and bilateral iliac arteries. The patient underwent a composite reconstruction using multi-visceral branched and bifurcated Dacron grafts. At 5 years from her last surgery, a CTA revealed no new dissection or further aneurysmal degenerations. Aortic disease in Marfan patients is a complex clinical problem that may lead to secondary or tertiary aortic reconstructions; close follow-up is mandatory.

Tratamento das afecções da aorta com a primeira geração de stents auto-expansíveis Aortic diseases treatment with a first generation of self expanding stent-grafts

Directory of Open Access Journals (Sweden)

Wagner Michael PEREIRA

2001-09-01

,57%, com 70,15% dos pacientes livre de eventos em 33 meses de seguimento, tornando o método factível e diminuindo a mortalidade no tratamento cirúrgico das dissecções agudas e crônicas do tipo B.INTRODUCTION: The authors describe the implantation of an endovascular self-expanding stents grafts at 33 months of follow-up. The use can be a new alternative for the treatment of descending aortic dissections and aneurysms disease. MATERIAL AND METHODS: From April 1998 to November 2000 (32 months, 37 endovascular stent grafts were implanted, 21 in acute dissections type B, 7 in acute dissections type A and 9 in chronic dissections type B and aneurysms ones. The age varied between 39 and 79 years (mean=57.94 ± 1.91 years, considering that 64.86% were male patients. The patients were submitted to median esternotomy, extracorporeal circulation (ECC, with deep hipothermia (18-20ºC, total circulatory arrest (TCA, and retrograde cerebral perfusion (RCP. The transverse aorta was incised and the stent was implanted in the descending proximal aorta with the aid sometimes of aortoscopy. The times of ECC, aortic clamping, TCA, RCP, rewarming, mechanic ventilation, hospitalization, trans and post-operative bleeding, blood replacement, events curve and survival curve were analyzed. RESULTS: The hospital mortality (30 days was 13.51%; 32 have been followed up from 1 to 33 months, 70.7% are free of events and survival curve with 63.19% (33 months. CONCLUSIONS: The implant of self-expanding intraluminal stent grafts presented has lower hospital mortality in the acute phase and follow-up in acute aortic dissections type B (10% than clinical treatment (IRAD. In spite of the small sample the procedure is promising and needs longer follow-up.

Expanding arch aneurysm causing a "kink" in a Bentall graft and heart failure.

Science.gov (United States)

Al-Mohaissen, Maha A; Skarsgard, Peter; Khoo, Clarence; Virani, Sean A; Munt, Brad; Leipsic, Jonathon; Ignaszewski, Andrew

2012-07-01

Marfan syndrome is associated with a high incidence of aortic root aneurysm and life-threatening aortic dissection. With the successful use of surgical aortic root replacement, dissection-related mortality has been significantly reduced. We present the case of a patient with Marfan syndrome who presented with heart failure secondary to an unusual graft-related complication 14 years after a Bentall procedure. Investigations revealed a supra-aortic stenosis resulting from a kink in the Bentall graft caused by pressure from an expanding aortic arch aneurysm. The patient underwent surgery with improvement in his ejection fraction and heart failure symptoms.

Dynamic Bifurcations

CERN Document Server

1991-01-01

Dynamical Bifurcation Theory is concerned with the phenomena that occur in one parameter families of dynamical systems (usually ordinary differential equations), when the parameter is a slowly varying function of time. During the last decade these phenomena were observed and studied by many mathematicians, both pure and applied, from eastern and western countries, using classical and nonstandard analysis. It is the purpose of this book to give an account of these developments. The first paper, by C. Lobry, is an introduction: the reader will find here an explanation of the problems and some easy examples; this paper also explains the role of each of the other paper within the volume and their relationship to one another. CONTENTS: C. Lobry: Dynamic Bifurcations.- T. Erneux, E.L. Reiss, L.J. Holden, M. Georgiou: Slow Passage through Bifurcation and Limit Points. Asymptotic Theory and Applications.- M. Canalis-Durand: Formal Expansion of van der Pol Equation Canard Solutions are Gevrey.- V. Gautheron, E. Isambe...

Inverse Relationship Between Membranous Septal Length and the Risk of Atrioventricular Block in Patients Undergoing Transcatheter Aortic Valve Implantation.

Science.gov (United States)

Hamdan, Ashraf; Guetta, Victor; Klempfner, Robert; Konen, Eli; Raanani, Ehud; Glikson, Michael; Goitein, Orly; Segev, Amit; Barbash, Israel; Fefer, Paul; Spiegelstein, Dan; Goldenberg, Ilan; Schwammenthal, Ehud

2015-08-17

This study sought to examine whether imaging of the atrioventricular (AV) membranous septum (MS) by computed tomography (CT) can be used to identify patient-specific anatomic risk of high-degree AV block and permanent pacemaker (PPM) implantation before transcatheter aortic valve implantation (TAVI) with self-expandable valves. MS length represents an anatomic surrogate of the distance between the aortic annulus and the bundle of His and may therefore be inversely related to the risk of conduction system abnormalities after TAVI. Seventy-three consecutive patients with severe aortic stenosis underwent contrast-enhanced CT before TAVI. The aortic annulus, aortic valve, and AV junction were assessed, and MS length was measured in the coronal view. In 13 patients (18%), high-degree AV block developed, and 21 patients (29%) received a PPM. Multivariable logistic regression analysis revealed MS length as the most powerful pre-procedural independent predictor of high-degree AV block (odds ratio [OR]: 1.35, 95% confidence interval [CI]: 1.1 to 1.7, p = 0.01) and PPM implantation (OR: 1.43, 95% CI: 1.1 to 1.8, p = 0.002). When taking into account pre- and post-procedural parameters, the difference between MS length and implantation depth emerged as the most powerful independent predictor of high-degree AV block (OR: 1.4, 95% CI: 1.2 to 1.7, p < 0.001), whereas the difference between MS length and implantation depth and calcification in the basal septum were the most powerful independent predictors of PPM implantation (OR: 1.39, 95% CI: 1.2 to 1.7, p < 0.001 and OR: 4.9, 95% CI: 1.2 to 20.5, p = 0.03; respectively). Short MS, insufficient difference between MS length and implantation depth, and the presence of calcification in the basal septum, factors that may all facilitate mechanical compression of the conduction tissue by the implanted valve, predict conduction abnormalities after TAVI with self-expandable valves. CT assessment of membranous septal anatomy provides

Nonlinear stability control and λ-bifurcation

International Nuclear Information System (INIS)

Erneux, T.; Reiss, E.L.; Magnan, J.F.; Jayakumar, P.K.

1987-01-01

Passive techniques for nonlinear stability control are presented for a model of fluidelastic instability. They employ the phenomena of λ-bifurcation and a generalization of it. λ-bifurcation occurs when a branch of flutter solutions bifurcates supercritically from a basic solution and terminates with an infinite period orbit at a branch of divergence solutions which bifurcates subcritically from the basic solution. The shape of the bifurcation diagram then resembles the greek letter λ. When the system parameters are in the range where flutter occurs by λ-bifurcation, then as the flow velocity increase the flutter amplitude also increases, but the frequencies of the oscillations decrease to zero. This diminishes the damaging effects of structural fatigue by flutter, and permits the flow speed to exceed the critical flutter speed. If generalized λ-bifurcation occurs, then there is a jump transition from the flutter states to a divergence state with a substantially smaller amplitude, when the flow speed is sufficiently larger than the critical flutter speed

Transcatheter Aortic Valve Implantation and Morbidity and Mortality-Related Factors: a 5-Year Experience in Brazil

Directory of Open Access Journals (Sweden)

André Luiz Silveira Souza

2016-01-01

Full Text Available Abstract Background: Transcatheter aortic valve implantation has become an option for high-surgical-risk patients with aortic valve disease. Objective: To evaluate the in-hospital and one-year follow-up outcomes of transcatheter aortic valve implantation. Methods: Prospective cohort study of transcatheter aortic valve implantation cases from July 2009 to February 2015. Analysis of clinical and procedural variables, correlating them with in-hospital and one-year mortality. Results: A total of 136 patients with a mean age of 83 years (80-87 underwent heart valve implantation; of these, 49% were women, 131 (96.3% had aortic stenosis, one (0.7% had aortic regurgitation and four (2.9% had prosthetic valve dysfunction. NYHA functional class was III or IV in 129 cases (94.8%. The baseline orifice area was 0.67 ± 0.17 cm2 and the mean left ventricular-aortic pressure gradient was 47.3±18.2 mmHg, with an STS score of 9.3% (4.8%-22.3%. The prostheses implanted were self-expanding in 97% of cases. Perioperative mortality was 1.5%; 30-day mortality, 5.9%; in-hospital mortality, 8.1%; and one-year mortality, 15.5%. Blood transfusion (relative risk of 54; p = 0.0003 and pulmonary arterial hypertension (relative risk of 5.3; p = 0.036 were predictive of in-hospital mortality. Peak C-reactive protein (relative risk of 1.8; p = 0.013 and blood transfusion (relative risk of 8.3; p = 0.0009 were predictive of 1-year mortality. At 30 days, 97% of patients were in NYHA functional class I/II; at one year, this figure reached 96%. Conclusion: Transcatheter aortic valve implantation was performed with a high success rate and low mortality. Blood transfusion was associated with higher in-hospital and one-year mortality. Peak C-reactive protein was associated with one-year mortality.

Clinical Outcomes of Self-Expandable Metal Stents for Malignant Rectal Obstruction.

Science.gov (United States)

Lee, Hyun Jung; Hong, Sung Pil; Cheon, Jae Hee; Kim, Tae Il; Kim, Won Ho; Park, Soo Jung

2018-01-01

Self-expandable metal stents are widely used to treat malignant colorectal obstruction. However, data on clinical outcomes of stent placement for rectal obstruction specifically are lacking. We aimed to investigate the clinical outcomes of self-expandable metal stents in malignant rectal obstruction in comparison with those in left colonic obstruction and to identify factors associated with clinical failure and complication. This was a retrospective study. The study was conducted at a tertiary care center. Between January 2005 and December 2013, medical charts of patients who underwent stent placement for malignant rectal or left colonic obstruction were reviewed retrospectively. Study intervention included self-expandable metal stent placement. Technical success, clinical success, and complications were measured. Technical success rates for the 2 study groups (rectum vs left colon, 93.5% vs 93.1%; p = 0.86) did not differ significantly; however, the clinical success rate was lower in patients with rectal obstruction (85.4% vs 92.1%; p = 0.02). In addition, the complication rate was higher in patients with rectal obstruction (37.4% vs 25.1%; p = 0.01). Patients with rectal obstruction showed higher rates of obstruction because of extracolonic malignancy (33.8% vs 15.8%; p stent use for palliation (78.6% vs 56.3%; p stent usage to be independent risk factors for clinical failure. Factors predictive of complications in the palliative group were total obstruction, obstruction because of extracolonic malignancy, and covered stent usage. This was a retrospective, single-center study. The efficacy and safety of stent placement for malignant rectal obstruction were comparable with those for left colonic obstruction. However, obstruction attributed to extracolonic malignancy, use of covered stents, and total obstruction negatively impacted clinical outcomes of self-expandable metal stent placement and must be considered by endoscopists. See Video Abstract at http

Transcatheter aortic valve implantation in patients with a mitral prosthesis; single center experience and review of literature.

Science.gov (United States)

Asil, Serkan; Şahiner, Levent; Özer, Necla; Kaya, E Barış; Evranos, Banu; Canpolat, Uğur; Yorgun, Hikmet; Karagöz, Heves; Aytemir, Kudret

2016-10-15

Following the encouraging results of several registries and trials, transcatheter aortic valve implantation (TAVI) has been recognized as a valid option in patients with severe aortic stenosis deemed at high or prohibitive risk for surgical treatment. Good procedural success and good clinical outcomes have been showed and very limited data exist on TAVI in the setting of a preexisting mitral prosthesis regarding the technique, potential complications, and outcomes. Here, we report six cases of transfemoral TAVI with a self-expanding bioprosthesis (CoreValve; Medtronic, Inc) in patients who had previously undergone mitral valve replacement. Preprocedural, intraprocedural ve postprocedural outcome and data were analyzed and a brief literature review is also presented. Our experiences show that transfemoral CoreValve implantation can be performed successfully in patients with mechanical and bioprosthetic mitral valves. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Anatomic changes of target vessels after fenestrated and branched aortic aneurysm repair.

Science.gov (United States)

Kalder, J; Keschenau, P; Tamm, M; Jalaie, H; Jacobs, M J; Greiner, A

2014-04-01

Objective of this study was to evaluate the anatomic changes of the stented target vessels after endovascular repair of complex aortic aneurysms. Between July 2011 and December 2013, 53 aortic aneurysms were treated in our department with fenestrated and branched stent-graft devices. Forty-two of these patients were pre- and postoperatively scanned with a high resolution computer tomography (CT) (Cook Zenith® fenestrated or branched, Australia Pty. Ltd., Brisbane, Australia: N.=19; AnacondaTM fenestrated, Vascutek, Glasgow, Scotland, UK: N.=23). The other 11 out of the 53 patients did not receive a CT scan, because of a pre-existing renal failure. In the CT scans we retrospectively evaluated the anatomic vessel deviation at the origin of the target vessel and the vessel shift distal to the stent. For the first measurement the CT scans were loaded into OsiriX MD®, and the pre- and postoperative angles of the target vessels were measured and subtracted. For matching, the CT-scans were normalized at vertebral body lumbar 2. The second measured angle was the maximal measured angle distal to the target vessel stent-graft. Altogether, 113 target vessels were stented (celiac trunk [CT] 15, superior mesenteric arteries [SMA] 26, renal arteries [RA] 72), with 97 balloon-expandable PTFE stents: 90 Atrium V12 (Maquet Getinge group, Hudson, NH, USA), 7 BeGrafts (Bentley InnoMed, Hechingen, Germany) and 16 self-expandable fluency PTFE stents (Bard, Karlsruhe, Germany). The mean anatomic deviation at the target vessel origin was 28±17.3 and the mean vessel shift distal to the stent was 36.3±18.8. There were no significant differences between the main device and the target vessel stent types. Fenestrated and branched stent-graft solutions for aortic aneurysm repair induce changes of the target vessel anatomy. We did not observe significant differences between the several devices.

Malignant biliary obstruction: percutaneous use of self-expandable stents

NARCIS (Netherlands)

Laméris, J. S.; Stoker, J.; Nijs, H. G.; Zonderland, H. M.; Terpstra, O. T.; van Blankenstein, M.; Schütte, H. E.

1991-01-01

A total of 83 self-expandable metallic stents were placed percutaneously in 69 patients for palliation of malignant biliary obstruction. Stent diameter was 1 cm; length, 3.5-10.5 cm. Of the 41 patients with common bile duct obstruction, 27 died 0.2-12 months (median, 3.2 months) after stent

Cadaveric aorta implantation for aortic graft infection.

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Ali, Asad; Bahia, Sandeep S S; Ali, Tahir

2016-01-01

This case report describes a 73-year-old gentleman who underwent explantation of an infected prosthetic aorto-iliac graft and replacement with a cryopreserved thoracic and aorto-iliac allograft. The patient has been followed up a for more than a year after surgery and remains well. After elective tube graft repair of his abdominal aortic aneurysm (AAA) in 2003, he presented to our unit in 2012 in cardiac arrest as a result of a rupture of the distal graft suture line due to infection. After resuscitation he underwent aorto-bifemoral grafting using a cuff of the original aortic graft proximally. Distally the new graft was anastomosed to his common femoral arteries, with gentamicin beads left in situ. Post discharge the patient was kept under close surveillance with serial investigations including nuclear scanning, however it became apparent that his new graft was infected and that he would require aortic graft replacement, an operation with a mortality of at least 50%. The patient underwent the operation and findings confirmed a synthetic graft infection. This tube graft was explanted and a cryopreserved aorta was used to the refashion the abdominal aorta and its bifurcation. The operation required a return to theatre day one post operatively for a bleeding side branch, which was repaired. The patient went on to make a full recovery stepping down from the intensive therapy unit day 6 post operatively and went on to be discharged 32 days after his cryopreserved aorta implantation. Copyright © 2016 The Author(s). Published by Elsevier Ltd.. All rights reserved.

Early recurrence of obstructive jaundice after placement of a self-expanding metal endoprosthesis

NARCIS (Netherlands)

Fockens, P.; Waxman, I.; Davids, P. H.; Huibregtse, K.; Tytgat, G. N.

1992-01-01

Self-expanding metal endoprostheses have ben used in the treatment of malignant obstructive jaundice for a few years. We report on a patient with obstructive jaundice due to a metastasis of a squamous cell lung cancer into the pancreatic head who received an expandable metal endoprosthesis and

Chimney Technique in Supra-Aortic Branch Reconstruction in China: A Systematic and Critical Review of Chinese Published Experience.

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Zhao, Yang; Shi, Yawei; Wang, Mian; Cui, Jin; Chen, Yitian; Zheng, Liang; Yin, Henghui; Chang, Guangqi

2017-08-01

The chimney graft (CG) technique has been proposed as a complete endovascular supra-aortic branch reconstruction for aortic pathologies. Due to the rapid growth of thoracic endovascular aortic repair (TEVAR) in China, we aimed to investigate the current data of the CG technique in this most populous country. Studies of supra-aortic branch reconstruction using the CG technique from Chinese centers were collected and analyzed. A total of 294 patients from Chinese centers who underwent TEVAR with CGs were included. There were 301 CGs performed, with a technical successful rate of 97.7%. The rate of early type I endoleaks was 7.1%, and the patency rate of the CGs was desirable. Balloon-expandable bare CGs were significantly associated with good early outcomes and a low rate of endoleaks. Current data from China revealed positive outcomes using CGs for supra-aortic branch reconstruction. Balloon-expandable bare CGs may be the first choice according to the data available but should be considered with caution.

Impact of Aortic Insufficiency on Ascending Aortic Dilatation and Adverse Aortic Events After Isolated Aortic Valve Replacement in Patients With a Bicuspid Aortic Valve.

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Wang, Yongshi; Wu, Boting; Li, Jun; Dong, Lili; Wang, Chunsheng; Shu, Xianhong

2016-05-01

Aberrant flow pattern and congenital fragility bestows bicuspid aortic valve (BAV) with a propensity toward ascending aorta dilatation, aneurysm, and dissection. Whether isolated aortic valve replacement (AVR) can prevent further dilatation in BAV ascending aorta and what indicates concurrent aortic intervention in the case of valve operation remain controversial. From June 2006 to January 2009, patients with a BAV who underwent isolated AVR were consecutively included and categorized into aortic insufficiency (BAV-AI, n = 84) and aortic stenosis (n = 112) groups, and another population of patients with a tricuspid aortic valve with aortic insufficiency (n = 149) was also recruited during the same period for comparison of annual aortic dilatation rate and adverse aortic events after isolated AVR. With a median follow-up period of 72 months (interquartile range, 66 to 78 months), ascending aorta dilatation rates were faster in the BAV-AI group than the BAV plus aortic stenosis and tricuspid aortic valve with aortic insufficiency groups (both p regression analysis identified aortic insufficiency (hazard ratio, 3.7; 95% confidence interval, 1.2 to 11.1; p = 0.019) as an independent risk factor for adverse aortic events among patients with BAV in general, whereas preoperative ascending aortic diameter larger than 45 mm (hazard ratio, 13.8; 95% confidence interval, 3.0 to 63.3; p = 0.001) served as a prognostic indicator in the BAV-AI group. An aggressive policy of preventive aortic interventions seemed appropriate in patients with BAV-AI during AVR, and BAV phenotype presenting as either insufficiency or stenosis should be taken into consideration when contemplating optimal surgical strategies for BAV aortopathy. Copyright © 2016 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.

Endovascular Treatment of Various Aortic Pathologies: Review of the Latest Data and Technologies.

Science.gov (United States)

Maeda, Koji; Ohki, Takao; Kanaoka, Yuji

2018-06-01

The technologies and innovations applicable to endovascular treatment for complex aortic pathologies have progressed rapidly over the last two decades. Although the initial outcomes of an endovascular aortic repair have been excellent, as long-term data became available, complications including endoleaks, endograft migration, and endograft infection have become apparent and are of concern. Previously, the indication for endovascular therapy was restricted to descending thoracic aortic aneurysms and abdominal aortic aneurysms. However, its indication has expanded along with the improvement of techniques and devices, and currently, it has become possible to treat pararenal aortic aneurysms and Crawford type 4 thoracoabdominal aortic aneurysm (TAAA) using the off-the-shelf devices. Additionally, custom-made devices allow for the treatment of arch or more extensive TAAAs. Endovascular treatment is applied not only to aneurysms but also to acute/chronic dissections. However, long-term outcomes are still unclear. This article provides an overview of available devices and the results of endovascular treatment for various aortic pathologies.

A self-adjusting expandable GPS collar for male elk

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Brian L. Dick; Scott L. Findholt; Bruce K. Johnson

2013-01-01

It is a challenge to use collars on male cervids because their neck size can increase substantially during the rut and also because of growth as the animal matures. We describe how to build a self-adjusting expandable collar for yearling or adult male Rocky Mountain elk (Cervus elaphus) to which very high frequency transmitters and global...

Bifurcation in a buoyant horizontal laminar jet

Science.gov (United States)

Arakeri, Jaywant H.; Das, Debopam; Srinivasan, J.

2000-06-01

The trajectory of a laminar buoyant jet discharged horizontally has been studied. The experimental observations were based on the injection of pure water into a brine solution. Under certain conditions the jet has been found to undergo bifurcation. The bifurcation of the jet occurs in a limited domain of Grashof number and Reynolds number. The regions in which the bifurcation occurs has been mapped in the Reynolds number Grashof number plane. There are three regions where bifurcation does not occur. The various mechanisms that prevent bifurcation have been proposed.

Bifurcations of Tumor-Immune Competition Systems with Delay

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Ping Bi

2014-01-01

Full Text Available A tumor-immune competition model with delay is considered, which consists of two-dimensional nonlinear differential equation. The conditions for the linear stability of the equilibria are obtained by analyzing the distribution of eigenvalues. General formulas for the direction, period, and stability of the bifurcated periodic solutions are given for codimension one and codimension two bifurcations, including Hopf bifurcation, steady-state bifurcation, and B-T bifurcation. Numerical examples and simulations are given to illustrate the bifurcations analysis and obtained results.

Percutaneous metallic self-expandable endoprostheses in malignant hilar biliary obstruction

NARCIS (Netherlands)

Stoker, J.; Laméris, J. S.; van Blankenstein, M.

1993-01-01

Forty-five patients with malignant hilar obstruction were treated with a total of 68 percutaneously inserted metallic self-expandable endoprostheses (Wallstents) for palliative biliary drainage. The stent diameter was 1 cm; the length was 3.5 to 10.5 cm. Early complications occurred in seven

Vascular geometry as a risk factor for non-penetrating traumatic injuries of the aortic arch.

Directory of Open Access Journals (Sweden)

Andreas Schicho

Full Text Available To assess biomechanical factors in aortic arch geometry contributing to the development of non-penetrating aortic arch injury (NAAI in multiply injured patients with an Injury Severity Score (ISS ≥ 16.230 consecutive multiply injured trauma patients with an ISS ≥ 16 admitted to our Level-I trauma center during a consecutive 24-month period were prospectively included of whom 13 presented with NAAI (5.7%. Standardized whole-body CT in a 2x128-detector-row scanner included a head-and-neck CTA. Aortic arch diameters, width, height, angles and thoracic width and height were measured in individuals with NAAI and ISS-, sex-, age-, and trauma mechanism-matched controls.There was no difference between groups regarding sex, age, ISS, and aortic diameters. The aortic arch angle in individuals with NAAI (71.3° ± 14.9° was larger than in healthy control (60.7° ± 8.6°; p*<0.05. In patients with NAAI, the distance between ascendent and descendent aorta was larger (5.2 cm ± 1.9 cm than in control (2.8 ± 0.5 cm; ***p<0.001. The aortic arch is higher above tracheal bifurcation in NAAI (3.6 cm ± 0.6 cm than in matched control (2.4 cm ± 0.3 cm; ***p<0.001. Accordingly, the area under the aortic arch, calculated as half of an eliptic shape, is significantly larger in patients with NAAI (15.0 cm2 ± 6.5 cm2 when compared to age- and sex-matched controls without NAAI (5.5 cm2 ± 1.3 cm2; ***p<0.001.Besides the magnitude of deceleration and direction of impact, width and height of the aortic arch are the 3rd and 4th factor directly contributing to the risk of developing traumatic NAAI in severely injured patients.

Recent perspective on coronary artery bifurcation interventions.

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Dash, Debabrata

2014-01-01

Coronary bifurcation lesions are frequent in routine practice, accounting for 15-20% of all lesions undergoing percutaneous coronary intervention (PCI). PCI of this subset of lesions is technically challenging and historically has been associated with lower procedural success rates and worse clinical outcomes compared with non-bifurcation lesions. The introduction of drug-eluting stents has dramatically improved the outcomes. The provisional technique of implanting one stent in the main branch remains the default approach in most bifurcation lesions. Selection of the most effective technique for an individual bifurcation is important. The use of two-stent techniques as an intention to treat is an acceptable approach in some bifurcation lesions. However, a large amount of metal is generally left unapposed in the lumen with complex two-stent techniques, which is particularly concerning for the risk of stent thrombosis. New technology and dedicated bifurcation stents may overcome some of the limitations of two-stent techniques and revolutionise the management of bifurcation PCI in the future.

Clinical efficacy of transcatheter aortic valve replacement for severe aortic stenosis in high-risk patients: the PREVAIL JAPAN trial.

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Sawa, Yoshiki; Takayama, Morimasa; Mitsudo, Kazuaki; Nanto, Shinsuke; Takanashi, Shuichiro; Komiya, Tatsuhiko; Kuratani, Toru; Tobaru, Tetsuya; Goto, Tsuyoshi

2015-01-01

Transcatheter aortic valve replacement (TAVR) is suggested to be less invasive and/or equally effective in comparison to conventional aortic valve replacement for high-risk symptomatic aortic stenosis patients. We herein report the initial results of a pivotal clinical trial of TAVR in Japan (the PREVAIL JAPAN). Sixty-four aortic stenosis patients (mean age 84.3 ± 6.1 years) not suitable for surgery were enrolled at three centers in Japan, with a primary composite endpoint of the 6-month post-procedure improvements in the aortic valve area and New York Heart Association (NYHA) functional classification. A transfemoral approach was used in 37 patients and a transapical approach was used in 27. The device success rate was 91.9 %. After 30 days and 6 months, the rates of mortality from any cause were 8.1 and 11.3 %, respectively. At 6 months, symptomatic stroke was found in 3.1 % of the patients, and silent infarction in 7.8 %. The aortic valve area and mean pressure gradient were significantly improved over time with both approaches (p < 0.001). At 6 months, the NYHA functional classification based on a conventional physician's assessment was improved in 87.9 % of the patients. We found results that were equivalent to those in other major TAVR trials, such as an acceptable 30-day survival (91.9 %), suggesting that balloon-expandable TAVR is effective for small Japanese AS patients classified as high-risk or inoperable.

Minimally Invasive Cardiac Surgery: Transapical Aortic Valve Replacement

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Ming Li

2012-01-01

Full Text Available Minimally invasive cardiac surgery is less traumatic and therefore leads to quicker recovery. With the assistance of engineering technologies on devices, imaging, and robotics, in conjunction with surgical technique, minimally invasive cardiac surgery will improve clinical outcomes and expand the cohort of patients that can be treated. We used transapical aortic valve implantation as an example to demonstrate that minimally invasive cardiac surgery can be implemented with the integration of surgical techniques and engineering technologies. Feasibility studies and long-term evaluation results prove that transapical aortic valve implantation under MRI guidance is feasible and practical. We are investigating an MRI compatible robotic surgical system to further assist the surgeon to precisely deliver aortic valve prostheses via a transapical approach. Ex vivo experimentation results indicate that a robotic system can also be employed in in vivo models.

Use of covered self-expandable stents for benign colorectal disorders in children.

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Lange, Bettina; Sold, Moritz; Kähler, Georg; Wessel, Lucas M; Kubiak, Rainer

2017-01-01

There is a lack of experience with covered self-expandable stents for benign colorectal disorders in children. Five children (4M, 1F) with a median age of 5years (range, 6months-9years) who underwent treatment with covered self-expandable plastic (SEPSs) or self-expandable metal stents (SEMSs) for a benign colorectal condition between April 2005 and November 2013 were recruited to this retrospective study. Etiologies included: anastomotic stricture with (n=1) or without (n=3) simultaneous enterocutaneous fistula, as well as an anastomotic leak associated with enterocutaneous fistula (n=1). All children suffered from either Hirschsprung's disease (n=3) or total colonic aganglionosis (Zuelzer-Wilson syndrome) (n=2). Median duration of individual stent placement was 23days (range, 1-87days). In all cases up to five different stents were placed over time. At follow-up two patients were successfully treated without further intervention. In another patient the anastomotic stricture resolved fully, but a coexisting enterocutaneous fistula persisted. Overall, three patients did not improve completely following stenting and required definite surgery. Stent-related problems were noted in all cases. There was one perforation of the colon at stent insertion. Further complications consisted of stent dislocation (n=4), obstruction (n=1), formation of granulation tissue (n=1), ulceration (n=1) and discomfort (n=3). Covered self-expandable stents enrich the armamentarium of interventions for benign colorectal disorders in children including anastomotic strictures and intestinal leaks. A stent can be applied either as an emergency procedure (bridge to surgery) or as an adjuvant treatment further to endoscopy and dilatation. Postinterventional problems are frequent but there is a potential for temporary or definite improvement following stent insertion. Copyright © 2017. Published by Elsevier Inc.

Aortic embolization of an Edwards SAPIEN prosthesis due to sigmoid left ventricular hypertrophy: Case report.

Science.gov (United States)

Yuksel, Isa Öner; Koklu, Erkan; Arslan, Sakir; Cagirci, Goksel; Kucukseymen, Selcuk

2016-06-01

Transcatheter aortic valve implantation (TAVI) is considered an alternative therapy in high-risk patients with severe aortic stenosis. Although a minimally invasive procedure, it is not free from complications, one of which is valve embolization at the time of TAVI. We present a case of embolization of a balloon-expandable aortic valve due to sigmoid left ventricular hypertrophy and managed with a second valve without surgery. The embolized valve was repositioned in the aortic arch between the left common carotid artery and the brachiocephalic trunk. Copyright © 2016 Sociedade Portuguesa de Cardiologia. Published by Elsevier España. All rights reserved.

Self-expanding nitinol stents for treatment of infragenicular arteries following unsuccessful balloon angioplasty

International Nuclear Information System (INIS)

Tepe, Gunnar; Heller, Stephan; Wiskirchen, Jakub; Fischmann, Arne; Claussen, Claus D.; Zeller, Thomas; Coerper, Stephan; Beckert, Stefan; Balletshofer, Bernd

2007-01-01

The feasibility of self-expanding nitinol stents for treatment of infragenicular arteries following unsuccessful balloon angioplasty was assessed. Options for lower limb percutaneous revascularization are limited, especially for complex vessel obstruction. Depending on the lesion and the experience of the interventionalist, the failure rate of balloon angioplasty (PTA) ranges between 10 and 40%. Until recently, no self-expanding stent for the use in the infragenicular arteries was available. This is the first report of the results for 18 consecutive patients who received 4F sheath compatible self-expanding nitinol stents following unsuccessful PTA or early restenosis. Twenty-four stents were implanted in 21 lesions for various indications residual stenosis >50% due to heavy calcification, flow-limiting dissection, occluding thrombus resistant to thrombolyis, thrombaspiration, and PTA, and early restenosis after previous PTA. Stent implantation was feasible in all cases. No complications occurred. After the stent implantation, all primarily unsuccessful interventions could be transformed into successful procedures with no residual stenosis >30% in any case. After 6 ± 2 months, two of the 18 patients died, and 14 of the 16 remaining patients improved clinically. At follow-up, the patency could be assessed in 14 stented arteries. Three stents were occluded, one stent showed some neointimal hyperplasia (50-70% restenosis), the remaining ten stents showed no restenosis (0-30%). The use of self-expanding nitinol stents in tibioperoneal and popliteal arteries is a safe and feasible option for the treatment of unsuccessful PTA. The 6-months patency is high. (orig.)

Bifurcation of the spin-wave equations

International Nuclear Information System (INIS)

Cascon, A.; Koiller, J.; Rezende, S.M.

1990-01-01

We study the bifurcations of the spin-wave equations that describe the parametric pumping of collective modes in magnetic media. Mechanisms describing the following dynamical phenomena are proposed: (i) sequential excitation of modes via zero eigenvalue bifurcations; (ii) Hopf bifurcations followed (or not) by Feingenbaum cascades of period doubling; (iii) local and global homoclinic phenomena. Two new organizing center for routes to chaos are identified; in the classification given by Guckenheimer and Holmes [GH], one is a codimension-two local bifurcation, with one pair of imaginary eigenvalues and a zero eigenvalue, to which many dynamical consequences are known; secondly, global homoclinic bifurcations associated to splitting of separatrices, in the limit where the system can be considered a Hamiltonian subjected to weak dissipation and forcing. We outline what further numerical and algebraic work is necessary for the detailed study following this program. (author)

Left ventricular hypertrophy in valvular aortic stenosis: mechanisms and clinical implications.

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Rader, Florian; Sachdev, Esha; Arsanjani, Reza; Siegel, Robert J

2015-04-01

Valvular aortic stenosis is the second most prevalent adult valve disease in the United States and causes progressive pressure overload, invariably leading to life-threatening complications. Surgical aortic valve replacement and, more recently, transcatheter aortic valve replacement effectively relieve the hemodynamic burden and improve the symptoms and survival of affected individuals. However, according to current American College of Cardiology/American Heart Association guidelines on the management of valvular heart disease, the indications for aortic valve replacement, including transcatheter aortic valve replacement, are based primarily on the development of clinical symptoms, because their presence indicates a dismal prognosis. Left ventricular hypertrophy develops in a sizeable proportion of patients before the onset of symptoms, and a growing body of literature demonstrates that regression of left ventricular hypertrophy resulting from aortic stenosis is incomplete after aortic valve replacement and associated with adverse early postoperative outcomes and worse long-term outcomes. Thus, reliance on the development of symptoms alone without consideration of structural abnormalities of the myocardium for optimal timing of aortic valve replacement potentially constitutes a missed opportunity to prevent postoperative morbidity and mortality from severe aortic stenosis, especially in the face of the quickly expanding indications of lower-risk transcatheter aortic valve replacement. The purpose of this review is to discuss the mechanisms and clinical implications of left ventricular hypertrophy in severe valvular aortic stenosis, which may eventually move to center stage as an indication for aortic valve replacement in the asymptomatic patient. Copyright © 2015 Elsevier Inc. All rights reserved.

Safety and efficacy of self-expandable metal stents for obstructive proximal and distal large bowel cancer.

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Mitra, V; Hu, M; Majumdar, D; Krishnan, V; Chaudhury, B; Hancock, J; Dwarakanath, D

2017-03-01

Self-expandable metal stents are often used to treat obstructive large bowel cancers. This study assessed the safety and efficacy of colonic stent insertion carried out in a district general hospital. Methods A retrospective review was carried out between 1 January 2007 and 28 February 2014 to identify patients who underwent stent insertion for malignant colorectal obstruction. Results Seventy-five patients (median age 75.2 years, 70.6% male) with primary colorectal cancer underwent stent insertion - 53 underwent semi-elective self-expanded metal stent insertion (for subacute bowel obstruction) and 22 had emergency stent inserted (for acute bowel obstruction). The majority (88%) had self-expanded metal stents inserted for palliation. Technical and clinical success rates were 98.7% and 91.2%, respectively. One patient had stent-related perforation; there was no procedure-related mortality. Conclusion This study shows that self-expanded metal stent insertion in malignant colorectal obstruction is safe and effective and can be successfully delivered in a district general hospital with high technical and clinical success rates.

Personal resources and satisfaction with life in Marfan syndrome patients with aortic pathology and in abdominal aortic aneurysm patients.

Science.gov (United States)

Stanišić, Michał-Goran; Rzepa, Teresa; Gawrońska, Alicja; Kubaszewski, Przemysław; Putowski, Maciej; Stefaniak, Sebastian; Perek, Bartłomiej

2018-03-01

Whether or not the source of aortic pathology is Marfan syndrome (MFS) or other processes leading to development of abdominal aorta aneurysms (AAA), the awareness of pathology may lead to an emotional upset and low assessment of satisfaction with life. To assess, in regard to MFS patients with aortic pathology and to abdominal aortic aneurysm patients: 1) whether or not self-efficacy (SE) and health locus of control (HLoC) affect the patients' satisfaction with life; 2) whether the two groups of patients differ in terms of mental dispositions. The study population consisted of 16 MFS patients with aortic pathology and 16 AAA patients, 9 men and 7 women in each group. The mean age of the MFS patients was 28.5 ±8.214, and of the AAA patients 64.25 ±7.019. The following scales were applied: Generalized Self-Efficacy Scale, Satisfaction With Life Scale, Multidimensional Health Locus of Control Scale. Abdominal aorta aneurysms patients compared to MFS patients gave a higher rating for SE ( MD = 33.94 and MD = 29.56), internal health locus of control ( MD = 25.00 and MD = 21.13), external personal HL o C ( MD = 24.50 and MD = 19.25), external impersonal HLoC ( MD = 23.06 and MD = 18.25), and satisfaction with life ( M = 22.06 and M = 20.13). Internal and external HL o C were significantly lower in MFS patients compared to AAA patients. In patients with aortic diseases, special attention must be paid to the state of personal resources (PR). Interactions made by medical professionals should focus on enhancing PR supporting the patients' self-knowledge on their SE. This will help to improve their satisfaction with life and form a positive attitude to the illness.

Stent valve implantation in conventional redo aortic valve surgery to prevent patient-prosthesis mismatch.

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Ferrari, Enrico; Franciosi, Giorgio; Clivio, Sara; Faletra, Francesco; Moccetti, Marco; Moccetti, Tiziano; Pedrazzini, Giovanni; Demertzis, Stefanos

2017-03-01

The goal was to show the technical details, feasibility and clinical results of balloon-expandable stent valve implantation in the aortic position during conventional redo open-heart surgery in selected obese patients with a small aortic prosthesis and severe patient-prosthesis mismatch. Two symptomatic overweight patients (body mass index of 31 and 38), each with a small aortic prosthesis (a 4-year-old, 21-mm Hancock II biological valve and a 29-year-old, 23-mm Duromedic mechanical valve), increased transvalvular gradients (59/31 and 74/44 mmHg) and a reduced indexed effective orifice area (0.50 and 0.43 cm 2 /m 2 ) underwent implantation of two 26-mm balloon-expandable Sapien 3 valves during standard on-pump redo valve surgery. Using full re-sternotomy, cardiopulmonary bypass and cardioplegic arrest, the two balloon-expandable stent valves were implanted under direct view using a standard aortotomy, after prosthesis removal and without annulus enlargement. Aortic cross-clamp times were 162 and 126 min; cardiopulmonary bypass times were 178 and 180 min; total surgical times were 360 and 318 min. At discharge, echocardiograms showed transvalvular peak and mean gradients of 13/9 and 23/13 mmHg and indexed effective orifice areas of 0.64 and 1.08 cm 2 /m 2 . The 3-month echocardiographic follow-up showed transvalvular peak and mean gradients of 18/9 and 19/11 mmHg and indexed effective orifice areas of 0.78 cm 2 /m 2 and 0.84 cm 2 /m 2 , with improved symptoms (New York Heart Association class 1). Implantation of a balloon-expandable stent valve during redo aortic valve surgery is feasible in selected cases and prevents patient-prosthesis mismatch in obese patients without need for aortic annulus enlargement. Moreover, in the case of stent valve degeneration, this approach permits additional valve-in-valve procedures with large stent valves and prevents re-redo surgery. © The Author 2016. Published by Oxford University Press on behalf of the

Quantification of progression and regression of descending thoracic aortic wall thickness by enhanced computed tomography

International Nuclear Information System (INIS)

Yokoyama, Kenichi; Takasu, Junichiro; Yamamoto, Rie; Taguchi, Rie; Itani, Yasutaka; Ito, Yuichi; Watanabe, Shigeru; Masuda, Yoshiaki

2001-01-01

The purpose of this study is to verify the usefulness of the quantification of aortic wall involvement by enhanced computed tomography (CT). One-hundred thirteen Japanese patients underwent two enhanced CT of the descending thoracic aorta at intervals. We sliced the descending thoracic aorta continuously from the level of the tracheal bifurcation with 1 cm intervals, and we defined aortic wall volume (AWV) (cm 3 ) as the sum of a 7-slice area of aortic wall involving calcification. The average of AWV increased from 7.95±2.92 cm 3 to 8.70±2.98 cm 3 . The developmental rate of AWV (ΔAWV) was 0.270±0.281 cm 3 /year. ΔAWV did not have a significant correlation with any risk factor at the baseline. ΔAWV had significant correlation with total cholesterol, (LDL-C) low-density lipoprotein cholesterol and LDL-C/(HDL-C) high-density lipoprotein cholesterol ratio at the follow-up, and by multivariate analysis with only the LDL-C/HDL-C ratio. ΔAWV was not correlated with the intake status of hypoglycemic, antihypertensive or lipid-lowering drugs. The cut-off level of total cholesterol with the most significant odds ratio for progression of aortic wall was 190 mg/dl, and that of LDL-C was 130 mg/dl. This method proved to be useful for the non-invasive assessment of aortic wall thickness. (author)

The bifurcations of nearly flat origami

Science.gov (United States)

Santangelo, Christian

Self-folding origami structures provide one means of fabricating complex, three-dimensional structures from a flat, two-dimensional sheet. Self-folding origami structures have been fabricated on scales ranging from macroscopic to microscopic and can have quite complicated structures with hundreds of folds arranged in complex patterns. I will describe our efforts to understand the mechanics and energetics of self-folding origami structures. Though the dimension of the configuration space of an origami structure scales with the size of the boundary and not with the number of vertices in the interior of the structure, a typical origami structure is also floppy in the sense that there are many possible ways to assign fold angles consistently. I will discuss our theoretical progress in understanding the geometry of the configuration space of origami. For random origami, the number of possible bifurcations grows surprisingly quickly even when the dimension of the configuration space is small. EFRI ODISSEI-1240441, DMR-0846582.

[Supra-aortic trunks occlusive disease: three different treatment approaches].

Science.gov (United States)

Dias, P; Almeida, P; Sampaio, S; Silva, A; Leite-Moreira, A; Pinho, P; Roncon de Albuquerque, R

2010-01-01

Unlike carotid bifurcation atherosclerotic stenosis, supra-aortic trunks (SAT) occlusive disease is rare and its revascularization uncommon, accouting for less than 10% of the operations performed on the extracranial brain-irrigating arteries. There are three different treatment approaches: transthoracic, extra-anatomic cervical and endovascular. Endovascular repair is gaining popularity as first-line therapy for proximal lesions with favorable anatomy because of its low morbidity and rare mortality. Extra-anatomic bypass is a safe and durable reconstruction and should be considered in patients with single vessel disease, with cardiopulmonary high-risk or with limited life expectancy. If cardiac surgery is needed, central transthoracic reconstruction is preferable, and the two procedures should be combined. The long-term patency of bypasses with aortic origin, specially when multiple vessels are involved, is superior to other repair techniques. We present three clinical cases that illustrate each of these therapeutic strategies: central brachiocephalic revascularization and synchronous cardiac surgery in a patient with complex SAT atherosclerosis disease; subclavian-carotid transposition for disabling upper limb claudication; and subclavian artery stenting for subclavian-steal syndrome. Surgical approach selection should be based on the individual patient's anatomy and operative risk.

Chiral symmetry breaking in QED3: bifurcation of the fermionic self-energy

International Nuclear Information System (INIS)

Almeida, L.D.; Natale, A.A.

1989-01-01

The existence of a bifurcation point in the Scwinger-Dyson equation of 2+1 dimensional quantum electrodynamics with N fermions, is studied. It is found an evidence for the existence of a critical behavior, such that chiral symmetry breaking may occur only for a small number of flavors. (author) [pt

Bifurcation and chaos in neural excitable system

International Nuclear Information System (INIS)

Jing Zhujun; Yang Jianping; Feng Wei

2006-01-01

In this paper, we investigate the dynamical behaviors of neural excitable system without periodic external current (proposed by Chialvo [Generic excitable dynamics on a two-dimensional map. Chaos, Solitons and Fractals 1995;5(3-4):461-79] and with periodic external current as system's parameters vary. The existence and stability of three fixed points, bifurcation of fixed points, the conditions of existences of fold bifurcation, flip bifurcation and Hopf bifurcation are derived by using bifurcation theory and center manifold theorem. The chaotic existence in the sense of Marotto's definition of chaos is proved. We then give the numerical simulated results (using bifurcation diagrams, computations of Maximum Lyapunov exponent and phase portraits), which not only show the consistence with the analytic results but also display new and interesting dynamical behaviors, including the complete period-doubling and inverse period-doubling bifurcation, symmetry period-doubling bifurcations of period-3 orbit, simultaneous occurrence of two different routes (invariant cycle and period-doubling bifurcations) to chaos for a given bifurcation parameter, sudden disappearance of chaos at one critical point, a great abundance of period windows (period 2 to 10, 12, 19, 20 orbits, and so on) in transient chaotic regions with interior crises, strange chaotic attractors and strange non-chaotic attractor. In particular, the parameter k plays a important role in the system, which can leave the chaotic behavior or the quasi-periodic behavior to period-1 orbit as k varies, and it can be considered as an control strategy of chaos by adjusting the parameter k. Combining the existing results in [Generic excitable dynamics on a two-dimensional map. Chaos, Solitons and Fractals 1995;5(3-4):461-79] with the new results reported in this paper, a more complete description of the system is now obtained

Hopf bifurcation in an Internet congestion control model

International Nuclear Information System (INIS)

Li Chunguang; Chen Guanrong; Liao Xiaofeng; Yu Juebang

2004-01-01

We consider an Internet model with a single link accessed by a single source, which responds to congestion signals from the network, and study bifurcation of such a system. By choosing the gain parameter as a bifurcation parameter, we prove that Hopf bifurcation occurs. The stability of bifurcating periodic solutions and the direction of the Hopf bifurcation are determined by applying the normal form theory and the center manifold theorem. Finally, a numerical example is given to verify the theoretical analysis

Stent impact on the geometry of the carotid bifurcation and the course of the internal carotid artery

International Nuclear Information System (INIS)

Berkefeld, J.; Zanella, F.E.; Rosendahl, H.; Theron, J.G.; Guimaraens, L.; Treggiari-Venzi, M.M.

2002-01-01

A measurement system is proposed to evaluate reconstructive effects of carotid stents on the geometry of the carotid bifurcation and the course of the internal carotid artery. To describe deviations of the stenotic internal carotid artery (ICA) from the extended axis of the common carotid artery (CCA) the CCA-ICA angle is measured between the CCA midaxis and the midaxis of the stenotic ICA segment. Maximal extensions of ICA tortuosities perpendicular to the course of the CCA axis are defined as ICA offset. The measurements were applied to DSA images of 224 carotid stenoses to evaluate variation and correlation between the two parameters. Comparative pre- and post-stent evaluation was performed in two series of 55 and 31 carotid stenoses treated with Wallstents and in a historic control group of 35 stenoses treated with Strecker stents. Straight course of the ICA was associated with low angle and low offset values, whereas tortuous course of the ICA showed larger angle and offset. A moderate linear correlation between the two parameters was found. Corresponding to a straightening of the stented segment, Wallstents reduced mean angle and offset values significantly. In five cases of the second series of Wallstents, transferrals of curves above the distal stent end associated with kinks were observed, and offset remained constant or increased. Strecker stent implantation caused no significant changes of bifurcational geometry. The proposed parameters corresponded to visual aspects of ICA tortuosity and detected reconstructive effects of self-expanding Wallstents on the ICA course. The measurement system may provide a basis for geometric evaluation of different stent types or implantation concepts with the aim: to optimize anatomic recanalization results in tortuous high angle-high offset bifurcations. (orig.)

Self-expandable metal stents in the treatment of benign anastomotic stricture after rectal resection for cancer.

Science.gov (United States)

Lamazza, A; Fiori, E; Sterpetti, A V; Schillaci, A; Scoglio, D; Lezoche, E

2014-04-01

To evaluate the use of self-expandable metallic stents to treat patients with symptomatic benign anastomotic stricture after colorectal resection. Ten patients with a benign symptomatic anastomotic stricture after colorectal resection were treated with endoscopic placement of a self-expandable metal stent. The stent was placed successfully in all 10 patients without any major morbidity. At a mean follow-up of 18 months the stenosis was resolved successfully in 7 out 10 patients (70%). The remaining three patients were subsequently treated successfully with balloon dilatation. Self-expandable metal stents represent a valid alternative to balloon dilatation to treat patients with benign symptomatic anastomotic stricture after colorectal resection for cancer. Colorectal Disease © 2013 The Association of Coloproctology of Great Britain and Ireland.

Multiple Re-entry Closures After TEVAR for Ruptured Chronic Post-dissection Thoraco-abdominal Aortic Aneurysm

Directory of Open Access Journals (Sweden)

R. Kinoshita

Full Text Available Introduction: Although thoracic endovascular aortic repair (TEVAR has become a promising treatment for complicated acute type B dissection, its role in treating chronic post-dissection thoraco-abdominal aortic aneurysm (TAA is still limited owing to persistent retrograde flow into the false lumen (FL through abdominal or iliac re-entry tears. Report: A case of chronic post-dissection TAA treatment, in which a dilated descending FL ruptured into the left thorax, is described. The primary entry tear was closed by emergency TEVAR and multiple abdominal re-entries were closed by EVAR. In addition, major re-entries at the detached right renal artery and iliac bifurcation were closed using covered stents. To close re-entries as far as possible, EVAR was carried out using the chimney technique, and additional aortic extenders were placed above the coeliac artery. A few re-entries remained, but complete FL thrombosis of the rupture site was achieved. Follow-up computed tomography showed significant shrinkage of the FL. Discussion: In treating post-dissection TAA, entry closure by TEVAR is sometimes insufficient, owing to persistent retrograde flow into the FL from abdominal or iliac re-entries. Adjunctive techniques are needed to close these distal re-entries to obtain complete FL exclusion, especially in rupture cases. Recently, encouraging results of complete coverage of the thoraco-abdominal aorta with fenestrated or branched endografts have been reported; however, the widespread employment of such techniques appears to be limited owing to technical difficulties. The present method with multiple re-entry closures using off the shelf and immediately available devices is an alternative for the endovascular treatment of post-dissection TAA, especially in the emergency setting. Keywords: Aortic dissection, Ruptured aortic aneurysm, Post-dissection thoracoabdominal aortic aneurysm, Endovascular aortic repair, Reentry closure, Endovascular procedures

Bioprosthetic Valve Fracture Improves the Hemodynamic Results of Valve-in-Valve Transcatheter Aortic Valve Replacement.

Science.gov (United States)

Chhatriwalla, Adnan K; Allen, Keith B; Saxon, John T; Cohen, David J; Aggarwal, Sanjeev; Hart, Anthony J; Baron, Suzanne J; Dvir, Danny; Borkon, A Michael

2017-07-01

Valve-in-valve (VIV) transcatheter aortic valve replacement (TAVR) may be less effective in small surgical valves because of patient/prosthesis mismatch. Bioprosthetic valve fracture (BVF) using a high-pressure balloon can be performed to facilitate VIV TAVR. We report data from 20 consecutive clinical cases in which BVF was successfully performed before or after VIV TAVR by inflation of a high-pressure balloon positioned across the valve ring during rapid ventricular pacing. Hemodynamic measurements and calculation of the valve effective orifice area were performed at baseline, immediately after VIV TAVR, and after BVF. BVF was successfully performed in 20 patients undergoing VIV TAVR with balloon-expandable (n=8) or self-expanding (n=12) transcatheter valves in Mitroflow, Carpentier-Edwards Perimount, Magna and Magna Ease, Biocor Epic and Biocor Epic Supra, and Mosaic surgical valves. Successful fracture was noted fluoroscopically when the waist of the balloon released and by a sudden drop in inflation pressure, often accompanied by an audible snap. BVF resulted in a reduction in the mean transvalvular gradient (from 20.5±7.4 to 6.7±3.7 mm Hg, P valve effective orifice area (from 1.0±0.4 to 1.8±0.6 cm 2 , P valves to facilitate VIV TAVR with either balloon-expandable or self-expanding transcatheter valves and results in reduced residual transvalvular gradients and increased valve effective orifice area. © 2017 American Heart Association, Inc.

Acute Aortic Arch Perforation During Transcatheter Aortic Valve Replacement in Bicuspid Aortic Stenosis and a Gothic Aortic Arch.

Science.gov (United States)

Millan-Iturbe, Oscar; Sawaya, Fadi J; Bieliauskas, Gintautas; Chow, Danny H F; De Backer, Ole; Søndergaard, Lars

2017-09-01

Transcatheter aortic valve replacement (TAVR) has evolved from a novel technology to an established therapy for high/intermediate-risk patients with severe symptomatic aortic stenosis (AS). Although TAVR is used to treat bicuspid severe AS, the large randomized trials typically excluded bicuspid AS because of its unique anatomic features. This case report describes an acute aortic perforation during delivery of a transcatheter heart valve to treat a severe bicuspid AS with a "gothic aortic arch"; more careful evaluation of the preprocedural multislice computed tomographic scan would have unveiled a sharply angulated aortic arch. This life-threatening complication was successfully treated by thoracic endovascular aortic repair. Copyright © 2017 Canadian Cardiovascular Society. Published by Elsevier Inc. All rights reserved.

Voltage stability, bifurcation parameters and continuation methods

Energy Technology Data Exchange (ETDEWEB)

Alvarado, F L [Wisconsin Univ., Madison, WI (United States)

1994-12-31

This paper considers the importance of the choice of bifurcation parameter in the determination of the voltage stability limit and the maximum power load ability of a system. When the bifurcation parameter is power demand, the two limits are equivalent. However, when other types of load models and bifurcation parameters are considered, the two concepts differ. The continuation method is considered as a method for determination of voltage stability margins. Three variants of the continuation method are described: the continuation parameter is the bifurcation parameter the continuation parameter is initially the bifurcation parameter, but is free to change, and the continuation parameter is a new `arc length` parameter. Implementations of voltage stability software using continuation methods are described. (author) 23 refs., 9 figs.

Role of fluoroscopic guided self expandable metallic stents in the management of malignant esophageal strictures

OpenAIRE

Mohamed Shaker; Ahmed Deif; Amr Abdelaal

2016-01-01

Objectives: To evaluate the role of fluoroscopic guided self expanding metallic stents in the management of dysphagia caused by malignant esophageal strictures. Materials and methods: During the period between April 2010 and October 2012, 31 patients with malignant esophageal strictures were subjected to fluoroscopic guided self expanding metallic stent application. The study included 22 males and 9 females ranging in age between 22 and 75 years old with mean age of 56.8 years. Lesions wer...

Novel self-expandable, stent-based transcatheter pulmonic valve: a preclinical animal study.

Science.gov (United States)

Kim, Gi Beom; Lim, Hong-Gook; Kim, Yong Jin; Choi, Eun Young; Kwon, Bo Sang; Jeong, Saeromi

2014-04-15

Because transcatheter implantation of pulmonary valve is indicated for limited-size dysfunctional right ventricular outflow tract only as a balloon-expandable stent, we investigated the feasibility of a large-diameter self-expandable valved stent and the durability of the valve after >6 months. We made a nitinol-wire-based, self-expandable valved stent with leaflets made from porcine pericardium. The porcine pericardium was treated with α-galactosidase, glutaraldehyde, and glycine after decellularization. After cutting the inguinal or cervical area, we implanted a valved stent in 12 sheep through the femoral or jugular vein by using an 18-Fr delivery catheter, controlling the catheter handles and hook block under fluoroscopic and echocardiographic guidance. The mean body weight of sheep was 43.9 kg. We successfully implanted valved stents (diameter: 24 mm in 7 sheep, 26 mm in 5 sheep) in good position in 8 sheep, in the main pulmonary artery (PA) in 2 sheep, and in the right ventricular outlet tract (RVOT) in 2 sheep. We sacrificed 8 sheep (6 sheep in good position, 1 sheep in the main PA, and 1 sheep in the RVOT) after >6 months. Five of the 6 sheep implanted in good position showed well-preserved valve morphology at the time of sacrifice. Histologic findings after routine sacrifice showed well-maintained collagen wave structure and no visible calcification in all explanted valve leaflets. Transcatheter implantation of a nitinol-wire-based, self-expandable valved stent in the pulmonic valve was feasible, and stents implanted in good position showed well-preserved valve leaflets with functional competence in the mid-term results. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Transcatheter Aortic Valve Replacement by a Novel Suprasternal Approach.

Science.gov (United States)

Codner, Pablo; Pugliese, Daniel; Kouz, Rémi; Patel, Amisha; Chen, Cheng-Han; Terre, Juan; Eudailey, Kyle W; Nazif, Tamim; Vahl, Torsten P; George, Isaac; Khalique, Omar K; Hahn, Rebecca T; Leon, Martin B; Kodali, Susheel; Borger, Michael

2018-04-01

Transcatheter aortic valve replacement (TAVR) provides therapy for patients with severe aortic stenosis at extreme, high, or intermediate surgical risk. Transfemoral access has been the preferred access route; however, this approach is not suitable for many TAVR candidates. A suprasternal approach may allow for earlier ambulation and shorter hospital stay as compared with other, nontransfemoral approaches. A total of 11 patients with unsuitable transfemoral access underwent suprasternal TAVR. Propensity matching was used to compare suprasternal patients to patients undergoing transaortic, transapical, and trans-subclavian TAVR. Groups were well matched for baseline characteristics. A self-expanding valve device was used in 6 (54.5%) and a balloon-expandable valve in 5 (45.5%) of the 11 patients treated by the suprasternal route. Suprasternal and trans-subclavian patients were able to ambulate earlier than patients treated by the transaortic route, a median 1.6 days (interquartile range [IQR]: 0.9 to 1.8), 1.6 days (IQR: 0.9 to 2.7), and 3.9 days (IQR: 1.9 to 4.5) after the procedure for suprasternal, trans-subclavian, and transaortic patients, respectively (p = 0.001). Length of hospitalization was shorter for patients treated by suprasternal or trans-subclavian access in comparison with patients treated by the transaortic or transapical approach: median 4 days (IQR: 3 to 8) and 4 days (IQR: 4 to 8) versus 8 days (IQR: 6 to 14) and 6 days (IQR: 7 to 11) for suprasternal and trans-subclavian versus transaortic and transapical, respectively (p = 0.01). Suprasternal and trans-subclavian access are associated with earlier ambulation and shorter hospitalization than other nontransfemoral TAVR routes, without an increase in complications. Further study is required to determine if suprasternal is the alternative access of choice for TAVR patients with poor transfemoral vasculature. Copyright © 2018 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights

Electrokinetic control of sample splitting at a channel bifurcation using isotachophoresis

International Nuclear Information System (INIS)

Persat, Alexandre; Santiago, Juan G

2009-01-01

We present a novel method for accurately splitting ionic samples at microchannel bifurcations. We leverage isotachophoresis (ITP) to focus and transport sample through a one-inlet, two-outlet microchannel bifurcation. We actively control the proportion of splitting by controlling potentials at end-channel reservoirs (and thereby controlling the current ratio). We explore the effect of buffer chemistry and local electric field on splitting dynamics and propose and validate a simple Kirchoff-type rule controlling the split ratio. We explore the effects of large applied electric fields on sample splitting and attribute a loss of splitting accuracy to electrohydrodynamic instabilities. We propose a scaling analysis to characterize the onset of this instability. This scaling is potentially useful for other electrokinetic flow problems with self-sharpening interfaces.

Pros and cons of transcatheter aortic valve implantation (TAVI).

Science.gov (United States)

Terré, Juan A; George, Isaac; Smith, Craig R

2017-09-01

Transcatheter aortic valve implantation (TAVI) or replacement (TAVR) was recently approved by the FDA for intermediate risk patients with severe aortic stenosis (AS). This technique was already worldwide adopted for inoperable and high-risk patients. Improved device technology, imaging analysis and operator expertise has reduced the initial worrisome higher complications rate associated with TAVR, making it comparable to surgical aortic valve replacement (SAVR). However, many answers need to be addressed before adoption in lower risk patients. This paper highlights the pros and cons of TAVI based mostly on randomized clinical trials involving the two device platforms approved in the United States. We focused our analysis on metrics that will play a key role in expanding TAVR indication in healthier individuals. We review the significance and gave a perspective on paravalvular leak (PVL), valve performance, valve durability, leaflet thrombosis, stroke and pacemaker requirement.

Model Reduction of Nonlinear Aeroelastic Systems Experiencing Hopf Bifurcation

KAUST Repository

Abdelkefi, Abdessattar

2013-06-18

In this paper, we employ the normal form to derive a reduced - order model that reproduces nonlinear dynamical behavior of aeroelastic systems that undergo Hopf bifurcation. As an example, we consider a rigid two - dimensional airfoil that is supported by nonlinear springs in the pitch and plunge directions and subjected to nonlinear aerodynamic loads. We apply the center manifold theorem on the governing equations to derive its normal form that constitutes a simplified representation of the aeroelastic sys tem near flutter onset (manifestation of Hopf bifurcation). Then, we use the normal form to identify a self - excited oscillator governed by a time - delay ordinary differential equation that approximates the dynamical behavior while reducing the dimension of the original system. Results obtained from this oscillator show a great capability to predict properly limit cycle oscillations that take place beyond and above flutter as compared with the original aeroelastic system.

Bifurcation Behavior Analysis in a Predator-Prey Model

Directory of Open Access Journals (Sweden)

Nan Wang

2016-01-01

Full Text Available A predator-prey model is studied mathematically and numerically. The aim is to explore how some key factors influence dynamic evolutionary mechanism of steady conversion and bifurcation behavior in predator-prey model. The theoretical works have been pursuing the investigation of the existence and stability of the equilibria, as well as the occurrence of bifurcation behaviors (transcritical bifurcation, saddle-node bifurcation, and Hopf bifurcation, which can deduce a standard parameter controlled relationship and in turn provide a theoretical basis for the numerical simulation. Numerical analysis ensures reliability of the theoretical results and illustrates that three stable equilibria will arise simultaneously in the model. It testifies the existence of Bogdanov-Takens bifurcation, too. It should also be stressed that the dynamic evolutionary mechanism of steady conversion and bifurcation behavior mainly depend on a specific key parameter. In a word, all these results are expected to be of use in the study of the dynamic complexity of ecosystems.

Bifurcation structure of a model of bursting pancreatic cells

DEFF Research Database (Denmark)

Mosekilde, Erik; Lading, B.; Yanchuk, S.

2001-01-01

One- and two-dimensional bifurcation studies of a prototypic model of bursting oscillations in pancreatic P-cells reveal a squid-formed area of chaotic dynamics in the parameter plane, with period-doubling bifurcations on one side of the arms and saddle-node bifurcations on the other. The transit......One- and two-dimensional bifurcation studies of a prototypic model of bursting oscillations in pancreatic P-cells reveal a squid-formed area of chaotic dynamics in the parameter plane, with period-doubling bifurcations on one side of the arms and saddle-node bifurcations on the other....... The transition from this structure to the so-called period-adding structure is found to involve a subcritical period-doubling bifurcation and the emergence of type-III intermittency. The period-adding transition itself is not smooth but consists of a saddle-node bifurcation in which (n + 1)-spike bursting...

NUMERICAL HOPF BIFURCATION OF DELAY-DIFFERENTIAL EQUATIONS

Institute of Scientific and Technical Information of China (English)

无

2006-01-01

In this paper we consider the numerical solution of some delay differential equations undergoing a Hopf bifurcation. We prove that if the delay differential equations have a Hopf bifurcation point atλ=λ*, then the numerical solution of the equation also has a Hopf bifurcation point atλh =λ* + O(h).

Repeat transcatheter aortic valve implantation using a latest generation balloon-expandable device for treatment of failing transcatheter heart valves.

Science.gov (United States)

Schaefer, Andreas; Treede, Hendrik; Seiffert, Moritz; Deuschl, Florian; Schofer, Niklas; Schneeberger, Yvonne; Blankenberg, Stefan; Reichenspurner, Hermann; Schaefer, Ulrich; Conradi, Lenard

2016-01-15

Paravalvular leakage (PVL) is a known complication of transcatheter aortic valve implantation (TAVI) and is associated with poor outcome. Besides balloon-post-dilatation, valve-in-valve (ViV) procedures can be taken into consideration to control this complication. Herein we present initial experience with use of the latest generation balloon-expandable Edwards Sapien 3® (S3) transcatheter heart valve (THV) for treatment of failing THVs. Between 01/2014 and 12/2014 three patients (two male, age: 71-80 y, log EUROScore I: 11.89 - 32.63) with failing THVs were refered to our institution for further treatment. THV approach with secondary implantation of an S3 was chosen after mutual agreement of the local interdisciplinary heart team at an interval of 533-1119 days from the index procedure. The performed procedures consisted of: S3 in Sapien XT, JenaValve and CoreValve. Successful transfemoral implantation with significant reduction of PVL was achieved in all cases. No intraprocedural complications occurred regarding placement of the S3 with a postprocedural effective orifice area (EOA) of 1.5-2.5 cm(2) and pressure gradients of max/mean 14/6-36/16 mmHg. 30-day mortality was 0%. At the latest follow-up of 90-530 days, all patients are alive and well with satisfactory THV function. Regarding VARC-2 criteria one major bleeding and one TIA was reported. In the instance of moderate or severe aortic regurgitation after TAVI, S3 ViV deployment is an excellent option to reduce residual regurgitation to none or mild. For further assertions concerning functional outcomes long-term results have to be awaited.

Bifurcation of solutions to Hamiltonian boundary value problems

Science.gov (United States)

McLachlan, R. I.; Offen, C.

2018-06-01

A bifurcation is a qualitative change in a family of solutions to an equation produced by varying parameters. In contrast to the local bifurcations of dynamical systems that are often related to a change in the number or stability of equilibria, bifurcations of boundary value problems are global in nature and may not be related to any obvious change in dynamical behaviour. Catastrophe theory is a well-developed framework which studies the bifurcations of critical points of functions. In this paper we study the bifurcations of solutions of boundary-value problems for symplectic maps, using the language of (finite-dimensional) singularity theory. We associate certain such problems with a geometric picture involving the intersection of Lagrangian submanifolds, and hence with the critical points of a suitable generating function. Within this framework, we then study the effect of three special cases: (i) some common boundary conditions, such as Dirichlet boundary conditions for second-order systems, restrict the possible types of bifurcations (for example, in generic planar systems only the A-series beginning with folds and cusps can occur); (ii) integrable systems, such as planar Hamiltonian systems, can exhibit a novel periodic pitchfork bifurcation; and (iii) systems with Hamiltonian symmetries or reversing symmetries can exhibit restricted bifurcations associated with the symmetry. This approach offers an alternative to the analysis of critical points in function spaces, typically used in the study of bifurcation of variational problems, and opens the way to the detection of more exotic bifurcations than the simple folds and cusps that are often found in examples.

Oversizing and Restenosis with Self-Expanding Stents in Iliofemoral Arteries

International Nuclear Information System (INIS)

Saguner, Ardan M.; Traupe, Tobias; Räber, Lorenz; Hess, Nina; Banz, Yara; Saguner, Arhan R.; Diehm, Nicolas; Hess, Otto M.

2012-01-01

Purpose: Uncoated self-expanding nitinol stents (NS) are commonly oversized in peripheral arteries. In current practice, 1-mm oversizing is recommended. Yet, oversizing of NS may be associated with increased restenosis. To provide further evidence, NS were implanted in porcine iliofemoral arteries with a stent-to-artery-ratio between 1.0 and 2.3. Besides conventional uncoated NS, a novel self-expanding NS with an antiproliferative titanium-nitride-oxide (TiNOX) coating was tested for safety and efficacy. Methods: Ten uncoated NS and six TiNOX-coated NS (5–6 mm) were implanted randomly in the iliofemoral artery of six mini-pigs. After implantation, quantitative angiography (QA) was performed for calculation of artery and minimal luminal diameter. Follow-up was performed by QA and histomorphometry after 5 months. Results: Stent migration, stent fracture, or thrombus formation were not observed. All stents were patent at follow-up. Based on the location of the stent (iliac/femoral) and the stent-to-artery-ratio, stent segments were divided into “normal-sized” (stent-to-artery-ratio < 1.4, n = 12) and “oversized” (stent-to-artery-ratio ≥ 1.4, n = 9). All stent segments expanded to their near nominal diameter during follow-up. Normal-sized stent segments increased their diameter by 6% and oversized segments by 29%. A significant correlation between oversizing and restenosis by both angiography and histomorphometry was observed. Restenosis rates were similar for uncoated NS and TiNOX-coated NS. Conclusions: TiNOX-coated NS are as safe and effective as uncoated NS in the porcine iliofemoral artery. All stents further expand to near their nominal diameter during follow-up. Oversizing is linearly and positively correlated with neointimal proliferation and restenosis, which may not be reduced by TiNOX-coating.

Energetics and monsoon bifurcations

Science.gov (United States)

Seshadri, Ashwin K.

2017-01-01

Monsoons involve increases in dry static energy (DSE), with primary contributions from increased shortwave radiation and condensation of water vapor, compensated by DSE export via horizontal fluxes in monsoonal circulations. We introduce a simple box-model characterizing evolution of the DSE budget to study nonlinear dynamics of steady-state monsoons. Horizontal fluxes of DSE are stabilizing during monsoons, exporting DSE and hence weakening the monsoonal circulation. By contrast latent heat addition (LHA) due to condensation of water vapor destabilizes, by increasing the DSE budget. These two factors, horizontal DSE fluxes and LHA, are most strongly dependent on the contrast in tropospheric mean temperature between land and ocean. For the steady-state DSE in the box-model to be stable, the DSE flux should depend more strongly on the temperature contrast than LHA; stronger circulation then reduces DSE and thereby restores equilibrium. We present conditions for this to occur. The main focus of the paper is describing conditions for bifurcation behavior of simple models. Previous authors presented a minimal model of abrupt monsoon transitions and argued that such behavior can be related to a positive feedback called the `moisture advection feedback'. However, by accounting for the effect of vertical lapse rate of temperature on the DSE flux, we show that bifurcations are not a generic property of such models despite these fluxes being nonlinear in the temperature contrast. We explain the origin of this behavior and describe conditions for a bifurcation to occur. This is illustrated for the case of the July-mean monsoon over India. The default model with mean parameter estimates does not contain a bifurcation, but the model admits bifurcation as parameters are varied.

The use of self expandable metallic stent in the management of malignant biliary obstruction

Energy Technology Data Exchange (ETDEWEB)

Han, Joon Koo; Choi, Byung Ihn; Chung, Jin Wook; Park, Jae Hyung; Han, Gi Seok; Han, Man Chung [Seoul National University College of Medicine, Seoul (Korea, Republic of)

1993-05-15

Self expandable metallic stent is a good alternative of percutaneous transhepatic biliary drainage because it can eliminate numerous problems caused by external drainage catheter, such as tube dislodgement, bile leakage and psychotic problems. Authors analyzed initial results of self expandable metallic stents used in the patient with malignant biliary obstruction to evaluate the efficacy of the procedure and to find the technical problems in the procedure. Self expandable metallic stents were inserted in 14 patients: three with recurrent stomach cancer: three with gallbladder cancer: seven with Klaskin tumor: one with common duct cancer. Gianturco type stent was used in 9 cases ans Wallstent was used in 2 cases. In remaining three case, both Z-stent and Wallstent were used in the same patient. The average period of follow up was 104 days (4-409 days). In 13 cases, the patency of the bile duct was restored by the stent (technical success: 92.9%). Occlusions of the stent were found in two cases, after two and 13 months, respectively. Causes of failure and stent occlusion were associated duodenal obstruction, tumor overgrowth and shortening of Wallstent. In remaining 11 patients, one patient was lost to follow up an 10 patients did not show recurrent jaundice until death or last follow up. There was no major complication related to the procedure. The insertion of self expandable metallic stent is a safe procedure and can eliminate major disadvantages of PTBD. Overstenting, overlapping and evaluation of associated GI tract obstruction is crucial for obtaining technical success and long-term patency.

The use of self expandable metallic stent in the management of malignant biliary obstruction

International Nuclear Information System (INIS)

Han, Joon Koo; Choi, Byung Ihn; Chung, Jin Wook; Park, Jae Hyung; Han, Gi Seok; Han, Man Chung

1993-01-01

Self expandable metallic stent is a good alternative of percutaneous transhepatic biliary drainage because it can eliminate numerous problems caused by external drainage catheter, such as tube dislodgement, bile leakage and psychotic problems. Authors analyzed initial results of self expandable metallic stents used in the patient with malignant biliary obstruction to evaluate the efficacy of the procedure and to find the technical problems in the procedure. Self expandable metallic stents were inserted in 14 patients: three with recurrent stomach cancer: three with gallbladder cancer: seven with Klaskin tumor: one with common duct cancer. Gianturco type stent was used in 9 cases ans Wallstent was used in 2 cases. In remaining three case, both Z-stent and Wallstent were used in the same patient. The average period of follow up was 104 days (4-409 days). In 13 cases, the patency of the bile duct was restored by the stent (technical success: 92.9%). Occlusions of the stent were found in two cases, after two and 13 months, respectively. Causes of failure and stent occlusion were associated duodenal obstruction, tumor overgrowth and shortening of Wallstent. In remaining 11 patients, one patient was lost to follow up an 10 patients did not show recurrent jaundice until death or last follow up. There was no major complication related to the procedure. The insertion of self expandable metallic stent is a safe procedure and can eliminate major disadvantages of PTBD. Overstenting, overlapping and evaluation of associated GI tract obstruction is crucial for obtaining technical success and long-term patency

Bifurcations of non-smooth systems

Science.gov (United States)

Angulo, Fabiola; Olivar, Gerard; Osorio, Gustavo A.; Escobar, Carlos M.; Ferreira, Jocirei D.; Redondo, Johan M.

2012-12-01

Non-smooth systems (namely piecewise-smooth systems) have received much attention in the last decade. Many contributions in this area show that theory and applications (to electronic circuits, mechanical systems, …) are relevant to problems in science and engineering. Specially, new bifurcations have been reported in the literature, and this was the topic of this minisymposium. Thus both bifurcation theory and its applications were included. Several contributions from different fields show that non-smooth bifurcations are a hot topic in research. Thus in this paper the reader can find contributions from electronics, energy markets and population dynamics. Also, a carefully-written specific algebraic software tool is presented.

Three-dimensional (3D) printing and its applications for aortic diseases.

Science.gov (United States)

Hangge, Patrick; Pershad, Yash; Witting, Avery A; Albadawi, Hassan; Oklu, Rahmi

2018-04-01

Three-dimensional (3D) printing is a process which generates prototypes from virtual objects in computer-aided design (CAD) software. Since 3D printing enables the creation of customized objects, it is a rapidly expanding field in an age of personalized medicine. We discuss the use of 3D printing in surgical planning, training, and creation of devices for the treatment of aortic diseases. 3D printing can provide operators with a hands-on model to interact with complex anatomy, enable prototyping of devices for implantation based upon anatomy, or even provide pre-procedural simulation. Potential exists to expand upon current uses of 3D printing to create personalized implantable devices such as grafts. Future studies should aim to demonstrate the impact of 3D printing on outcomes to make this technology more accessible to patients with complex aortic diseases.

A non-contrast self-navigated 3-dimensional MR technique for aortic root and vascular access route assessment in the context of transcatheter aortic valve replacement: proof of concept

Energy Technology Data Exchange (ETDEWEB)

Renker, Matthias [Medical University of South Carolina, Heart and Vascular Center, Charleston, SC (United States); University Hospital Giessen and Marburg, Department of Medicine I, Giessen (Germany); Varga-Szemes, Akos; Rier, Jeremy D.; Steinberg, Daniel H. [Medical University of South Carolina, Heart and Vascular Center, Charleston, SC (United States); Schoepf, U.J. [Medical University of South Carolina, Heart and Vascular Center, Charleston, SC (United States); Medical University of South Carolina, Department of Radiology and Radiological Science, Charleston, SC (United States); Baumann, Stefan [Medical University of South Carolina, Heart and Vascular Center, Charleston, SC (United States); University of Heidelberg, 1st Department of Medicine, Faculty of Medicine Mannheim, University Medical Centre Mannheim (UMM), Mannheim (Germany); Piccini, Davide [Siemens Healthcare IM BM PI, Advanced Clinical Imaging Technology, Lausanne (Switzerland); University Hospital (CHUV) and University of Lausanne (UNIL), Department of Radiology, Lausanne (Switzerland); Zenge, Michael O.; Mueller, Edgar [Siemens AG Healthcare Sector, Erlangen (Germany); Rehwald, Wolfgang G. [Duke University Medical Center, Cardiovascular MR Center, Durham, NC (United States); Moellmann, Helge [Kerckhoff Heart and Thorax Center, Bad Nauheim (Germany); Hamm, Christian W. [University Hospital Giessen and Marburg, Department of Medicine I, Giessen (Germany); De Cecco, Carlo N. [Medical University of South Carolina, Heart and Vascular Center, Charleston, SC (United States); University of Rome ' ' Sapienza' ' -Polo Pontino, Department of Radiological Sciences, Oncology and Pathology, Latina (Italy)

2016-04-15

Due to the high prevalence of renal failure in transcatheter aortic valve replacement (TAVR) candidates, a non-contrast MR technique is desirable for pre-procedural planning. We sought to evaluate the feasibility of a novel, non-contrast, free-breathing, self-navigated three-dimensional (SN3D) MR sequence for imaging the aorta from its root to the iliofemoral run-off in comparison to non-contrast two-dimensional-balanced steady-state free-precession (2D-bSSFP) imaging. SN3D [field of view (FOV), 220-370 mm{sup 3}; slice thickness, 1.15 mm; repetition/echo time (TR/TE), 3.1/1.5 ms; and flip angle, 115 ] and 2D-bSSFP acquisitions (FOV, 340 mm; slice thickness, 6 mm; TR/TE, 2.3/1.1 ms; flip angle, 77 ) were performed in 10 healthy subjects (all male; mean age, 30.3 ± 4.3 yrs) using a 1.5-T MRI system. Aortic root measurements and qualitative image ratings (four-point Likert-scale) were compared. The mean effective aortic annulus diameter was similar for 2D-bSSFP and SN3D (26.7 ± 0.7 vs. 26.1 ± 0.9 mm, p = 0.23). The mean image quality of 2D-bSSFP (4; IQR 3-4) was rated slightly higher (p = 0.03) than SN3D (3; IQR 2-4). The mean total acquisition time for SN3D imaging was 12.8 ± 2.4 min. Our results suggest that a novel SN3D sequence allows rapid, free-breathing assessment of the aortic root and the aortoiliofemoral system without administration of contrast medium. (orig.)

A non-contrast self-navigated 3-dimensional MR technique for aortic root and vascular access route assessment in the context of transcatheter aortic valve replacement: proof of concept

International Nuclear Information System (INIS)

Renker, Matthias; Varga-Szemes, Akos; Rier, Jeremy D.; Steinberg, Daniel H.; Schoepf, U.J.; Baumann, Stefan; Piccini, Davide; Zenge, Michael O.; Mueller, Edgar; Rehwald, Wolfgang G.; Moellmann, Helge; Hamm, Christian W.; De Cecco, Carlo N.

2016-01-01

Due to the high prevalence of renal failure in transcatheter aortic valve replacement (TAVR) candidates, a non-contrast MR technique is desirable for pre-procedural planning. We sought to evaluate the feasibility of a novel, non-contrast, free-breathing, self-navigated three-dimensional (SN3D) MR sequence for imaging the aorta from its root to the iliofemoral run-off in comparison to non-contrast two-dimensional-balanced steady-state free-precession (2D-bSSFP) imaging. SN3D [field of view (FOV), 220-370 mm 3 ; slice thickness, 1.15 mm; repetition/echo time (TR/TE), 3.1/1.5 ms; and flip angle, 115 ] and 2D-bSSFP acquisitions (FOV, 340 mm; slice thickness, 6 mm; TR/TE, 2.3/1.1 ms; flip angle, 77 ) were performed in 10 healthy subjects (all male; mean age, 30.3 ± 4.3 yrs) using a 1.5-T MRI system. Aortic root measurements and qualitative image ratings (four-point Likert-scale) were compared. The mean effective aortic annulus diameter was similar for 2D-bSSFP and SN3D (26.7 ± 0.7 vs. 26.1 ± 0.9 mm, p = 0.23). The mean image quality of 2D-bSSFP (4; IQR 3-4) was rated slightly higher (p = 0.03) than SN3D (3; IQR 2-4). The mean total acquisition time for SN3D imaging was 12.8 ± 2.4 min. Our results suggest that a novel SN3D sequence allows rapid, free-breathing assessment of the aortic root and the aortoiliofemoral system without administration of contrast medium. (orig.)

Bifurcations of a class of singular biological economic models

International Nuclear Information System (INIS)

Zhang Xue; Zhang Qingling; Zhang Yue

2009-01-01

This paper studies systematically a prey-predator singular biological economic model with time delay. It shows that this model exhibits two bifurcation phenomena when the economic profit is zero. One is transcritical bifurcation which changes the stability of the system, and the other is singular induced bifurcation which indicates that zero economic profit brings impulse, i.e., rapid expansion of the population in biological explanation. On the other hand, if the economic profit is positive, at a critical value of bifurcation parameter, the system undergoes a Hopf bifurcation, i.e., the increase of delay destabilizes the system and bifurcates into small amplitude periodic solution. Finally, by using Matlab software, numerical simulations illustrate the effectiveness of the results obtained here. In addition, we study numerically that the system undergoes a saddle-node bifurcation when the bifurcation parameter goes through critical value of positive economic profit.

Tissue expander stimulated lengthening of arteries (TESLA) induces early endothelial cell proliferation in a novel rodent model.

Science.gov (United States)

Potanos, Kristina; Fullington, Nora; Cauley, Ryan; Purcell, Patricia; Zurakowski, David; Fishman, Steven; Vakili, Khashayar; Kim, Heung Bae

2016-04-01

We examine the mechanism of aortic lengthening in a novel rodent model of tissue expander stimulated lengthening of arteries (TESLA). A rat model of TESLA was examined with a single stretch stimulus applied at the time of tissue expander insertion with evaluation of the aorta at 2, 4 and 7day time points. Measurements as well as histology and proliferation assays were performed and compared to sham controls. The aortic length was increased at all time points without histologic signs of tissue injury. Nuclear density remained unchanged despite the increase in length suggesting cellular hyperplasia. Cellular proliferation was confirmed in endothelial cell layer by Ki-67 stain. Aortic lengthening may be achieved using TESLA. The increase in aortic length can be achieved without tissue injury and results at least partially from cellular hyperplasia. Further studies are required to define the mechanisms involved in the growth of arteries under increased longitudinal stress. Copyright © 2015 Elsevier Inc. All rights reserved.

Stent Fracture and Reocclusion After Placement of a Single Self-Expanding Stent in the Common Iliac Artery and Endovascular Treatment

International Nuclear Information System (INIS)

Higashiura, Wataru; Sakaguchi, Shoji; Morimoto, Kengo; Kichikawa, Kimihiko

2008-01-01

We present a case of fracture of a single self-expanding stent placed in the common iliac artery (CIA). An 80-year-old woman underwent placement of a self-expanding stent for CIA occlusion. Stent fracture and reocclusion were detected after 18 months. Successful revascularization was achieved using a stent-in-stent maneuver. The possibility of stent fracture with reocclusion should be considered following treatment with a single self-expanding stent for CIA occlusion.

Analysis of Vehicle Steering and Driving Bifurcation Characteristics

Directory of Open Access Journals (Sweden)

Xianbin Wang

2015-01-01

Full Text Available The typical method of vehicle steering bifurcation analysis is based on the nonlinear autonomous vehicle model deriving from the classic two degrees of freedom (2DOF linear vehicle model. This method usually neglects the driving effect on steering bifurcation characteristics. However, in the steering and driving combined conditions, the tyre under different driving conditions can provide different lateral force. The steering bifurcation mechanism without the driving effect is not able to fully reveal the vehicle steering and driving bifurcation characteristics. Aiming at the aforementioned problem, this paper analyzed the vehicle steering and driving bifurcation characteristics with the consideration of driving effect. Based on the 5DOF vehicle system dynamics model with the consideration of driving effect, the 7DOF autonomous system model was established. The vehicle steering and driving bifurcation dynamic characteristics were analyzed with different driving mode and driving torque. Taking the front-wheel-drive system as an example, the dynamic evolution process of steering and driving bifurcation was analyzed by phase space, system state variables, power spectral density, and Lyapunov index. The numerical recognition results of chaos were also provided. The research results show that the driving mode and driving torque have the obvious effect on steering and driving bifurcation characteristics.

Bifurcation scenarios for bubbling transition.

Science.gov (United States)

Zimin, Aleksey V; Hunt, Brian R; Ott, Edward

2003-01-01

Dynamical systems with chaos on an invariant submanifold can exhibit a type of behavior called bubbling, whereby a small random or fixed perturbation to the system induces intermittent bursting. The bifurcation to bubbling occurs when a periodic orbit embedded in the chaotic attractor in the invariant manifold becomes unstable to perturbations transverse to the invariant manifold. Generically the periodic orbit can become transversely unstable through a pitchfork, transcritical, period-doubling, or Hopf bifurcation. In this paper a unified treatment of the four types of bubbling bifurcation is presented. Conditions are obtained determining whether the transition to bubbling is soft or hard; that is, whether the maximum burst amplitude varies continuously or discontinuously with variation of the parameter through its critical value. For soft bubbling transitions, the scaling of the maximum burst amplitude with the parameter is derived. For both hard and soft transitions the scaling of the average interburst time with the bifurcation parameter is deduced. Both random (noise) and fixed (mismatch) perturbations are considered. Results of numerical experiments testing our theoretical predictions are presented.

Attractors near grazing–sliding bifurcations

International Nuclear Information System (INIS)

Glendinning, P; Kowalczyk, P; Nordmark, A B

2012-01-01

In this paper we prove, for the first time, that multistability can occur in three-dimensional Fillipov type flows due to grazing–sliding bifurcations. We do this by reducing the study of the dynamics of Filippov type flows around a grazing–sliding bifurcation to the study of appropriately defined one-dimensional maps. In particular, we prove the presence of three qualitatively different types of multiple attractors born in grazing–sliding bifurcations. Namely, a period-two orbit with a sliding segment may coexist with a chaotic attractor, two stable, period-two and period-three orbits with a segment of sliding each may coexist, or a non-sliding and period-three orbit with two sliding segments may coexist

Bifurcation with memory

International Nuclear Information System (INIS)

Olmstead, W.E.; Davis, S.H.; Rosenblat, S.; Kath, W.L.

1986-01-01

A model equation containing a memory integral is posed. The extent of the memory, the relaxation time lambda, controls the bifurcation behavior as the control parameter R is increased. Small (large) lambda gives steady (periodic) bifurcation. There is a double eigenvalue at lambda = lambda 1 , separating purely steady (lambda 1 ) from combined steady/T-periodic (lambda > lambda 1 ) states with T → infinity as lambda → lambda + 1 . Analysis leads to the co-existence of stable steady/periodic states and as R is increased, the periodic states give way to the steady states. Numerical solutions show that this behavior persists away from lambda = lambda 1

A case study in bifurcation theory

Science.gov (United States)

Khmou, Youssef

This short paper is focused on the bifurcation theory found in map functions called evolution functions that are used in dynamical systems. The most well-known example of discrete iterative function is the logistic map that puts into evidence bifurcation and chaotic behavior of the topology of the logistic function. We propose a new iterative function based on Lorentizan function and its generalized versions, based on numerical study, it is found that the bifurcation of the Lorentzian function is of second-order where it is characterized by the absence of chaotic region.

Accidental Coverage of Both Renal Arteries during Infrarenal Aortic Stent-Graft Implantation: Cause and Treatment

Directory of Open Access Journals (Sweden)

Umberto Marcello Bracale

2014-01-01

Full Text Available The purpose of this paper is to report a salvage maneuver for accidental coverage of both renal arteries during endovascular aneurysm repair (EVAR of an infrarenal abdominal aortic aneurysm (AAA. A 72-year-old female with a 6 cm infrarenal abdominal aortic aneurysm was treated by endovascular means with a standard bifurcated graft. Upon completing an angiogram, both renal arteries were found to be accidentally occluded. Through a left percutaneous brachial approach, the right renal artery was catheterized and a chimney stent was deployed; however this was not possible for the left renal artery. A retroperitoneal surgical approach was therefore carried out with a retrograde chimney stent implanted to restore blood flow. After three months, both renal arteries were patent and renal function was not different from the baseline. Both endovascular with percutaneous access via the brachial artery and open retroperitoneal approaches with retrograde catheterization are feasible rescue techniques to recanalize the accidentally occluded renal arteries during EVAR.

Aortic insufficiency

Science.gov (United States)

... page, please enable JavaScript. Aortic insufficiency is a heart valve disease in which the aortic valve does not close ... aortic insufficiency Images Aortic insufficiency References Carabello BA. Valvular heart disease. In: Goldman L, Schafer AI, eds. Goldman-Cecil ...

Tube Stent-Grafts for Infrarenal Aortic Aneurysm: A Matched-Paired Analysis Based on EUROSTAR Data

International Nuclear Information System (INIS)

Ruppert, Volker; Leurs, Lina J.; Hobo, Roel; Buth, Jacob; Rieger, Johannes; Umscheid, Thomas

2007-01-01

Objective. Tube stent-grafts for treatment of infrarenal aortic aneurysms (AAAs) are a nearly forgotten concept. For focal aortic pathologies tube stent-grafts may be a treatment option. We have performed a retrospective matched-paired analysis of the EUROSTAR registry regarding the outcome of tube vs. bifurcated stent-grafts for AAA. Tapered aortomonoiliac stent-grafts were not the objective of this study. Materials and methods. From July 1997 to June 2006, 7581 patients who underwent an endovascular AAA repair were entered in the EUROSTAR registry by 164 centers. One hundred fifty-three patients were treated with tube stent-grafts. For each of these 153 patients we selected one patient from a bifurcated stent-graft group (BGG-original, 7428 patients) matched according to gender, ASA, age, AAA diameter, and type of anesthesia. Differences in preoperative details between the two study groups were analyzed using chi-square test for discrete variables and Wilcoxon rank-sum test for continuous variables. Multivariate logistic regression analysis was performed on early complications. Midterm outcomes (>30 days) were analyzed by Kaplan-Meier and multivariate Cox proportional hazard model. Results. The duration of the procedure was shorter in the tube stent-graft group (TGG; 102.3 ± 52.2) than in BGG (128.3 ± 55.0; p 0.0002). Type II endoleak was less frequent in TGG (4.0%; mean follow-up, 23.12 ± 23.9 months) than in BGG (14.3%; mean follow-up, 20.77 ± 20.0 months; p = 0.0394). Type I endoleaks and migration were distributed equally, without significant differences between the groups. Combined 30-day and late mortality was higher for TGG (p = 0.0346) and was obviously not aneurysm related. Conclusions. We conclude that after selection of patients, tube stent-grafts for infrarenal aortic repair can be performed with great safety regarding endoleaks and migration. The combined higher 30-day mortality and non-aneurysm-related mortality during follow-up were mainly

Bifurcation structure of a model of bursting pancreatic cells

DEFF Research Database (Denmark)

Mosekilde, Erik; Lading, B.; Yanchuk, S.

2001-01-01

. The transition from this structure to the so-called period-adding structure is found to involve a subcritical period-doubling bifurcation and the emergence of type-III intermittency. The period-adding transition itself is not smooth but consists of a saddle-node bifurcation in which (n + 1)-spike bursting...... behavior is born, slightly overlapping with a subcritical period-doubling bifurcation in which n-spike bursting behavior loses its stability.......One- and two-dimensional bifurcation studies of a prototypic model of bursting oscillations in pancreatic P-cells reveal a squid-formed area of chaotic dynamics in the parameter plane, with period-doubling bifurcations on one side of the arms and saddle-node bifurcations on the other...

High-risk Trans-Catheter Aortic Valve Replacement in a Failed Freestyle Valve with Low Coronary Height: A Case Report.

Science.gov (United States)

Karimi, Ashkan; Pourafshar, Negiin; Dibu, George; Beaver, Thomas M; Bavry, Anthony A

2017-06-01

A 55-year-old male with a history of two prior cardiac surgeries presented with decompensated heart failure due to severe bioprosthetic aortic valve insufficiency. A third operation was viewed prohibitively high risk and valve-in-valve trans-catheter aortic valve replacement was considered. There were however several high-risk features and technically challenging aspects including low coronary ostia height, poor visualization of the aortic sinuses, and difficulty in identification of the coplanar view due to severe aortic insufficiency, and a highly mobile aortic valve mass. After meticulous peri-procedural planning, trans-catheter aortic valve replacement was carried out with a SAPIEN 3 balloon-expandable valve without any complication. Strategies undertaken to navigate the technically challenging aspects of the case are discussed.

Early results of valve-sparing ascending aortic replacement in type A aortic dissection and aortic insufficiency

Directory of Open Access Journals (Sweden)

М. Л. Гордеев

2016-08-01

Full Text Available Aim: The study was designed to investigate predictors of effective valve-sparing ascending aortic replacement in patients with Stanford type A aortic dissection combined with aortic insufficiency and to analyze efficacy and safety of this kind of surgery.Methods: From January 2010 to December 2015, 49 patients with Stanford type A aortic dissection combined with aortic insufficiency underwent ascending aortic replacement. All patients were divided into 3 groups: valve-sparing procedures (group 1, n = 11, combined aortic valve and supracoronary ascending aortic replacement (group 2, n = 12, and Bentall procedure (group 3, n = 26. We assessed the initial status of patients, incidence of complications and efficacy of valve-sparing ascending aortic replacement.Results: The hospital mortality rate was 8.2% (4/49 patients. The amount of surgical correction correlated with the initial diameter of the aorta at the level of the sinuses of Valsalva. During the hospital period, none of patients from group 1 developed aortic insufficiency exceeding Grade 2 and the vast majority of patients had trivial aortic regurgitation. The parameters of cardiopulmonary bypass, cross-clamp time and circulatory arrest time did not correlate with the initial size of the ascending aorta and aortic valve blood flow impairment, neither did they influence significantly the incidence and severity of neurological complications. The baseline size of the ascending aorta and degree of aortic regurgitation did not impact the course of the early hospital period.Conclusions: Supracoronary ascending aortic replacement combined with aortic valve repair in ascending aortic dissection and aortic regurgitation is effective and safe. The initial size of the ascending aorta and aortic arch do not influence immediate results. The diameter of the aorta at the level of the sinuses of Valsalva and the condition of aortic valve leaflets could be considered as the limiting factors. Further long

Self expandable polytetrafluoroethylene stent for carotid blowout syndrome.

Science.gov (United States)

Tatar, E C; Yildirim, U M; Dündar, Y; Ozdek, A; Işik, E; Korkmaz, H

2012-01-01

Carotid blowout syndrome (CBS) is an emergency complication in patients undergoing treatment for head and neck cancers. The classical management of CBS is the ligation of the common carotid artery, because suturing is not be possible due to infection and necrosis of the field. In this case report, we present a patient with CBS, in whom we applied a self-expandable polytetrafluoroethylene (PTFE) stent and observed no morbidity. Endovascular stent is a life-saving technique with minimum morbidity that preserves blood flow to the brain. We believe that this method is preferable to ligation of the artery in CBS.

Formation of shatter cones by symmetric fracture bifurcation: Phenomenological modeling and validation

Science.gov (United States)

Kenkmann, Thomas; Hergarten, Stefan; Kuhn, Thomas; Wilk, Jakob

2016-08-01

Several models of shatter cone formation require a heterogeneity at the cone apex of high impedance mismatch to the surrounding bulk rock. This heterogeneity is the source of spherically expanding waves that interact with the planar shock front or the following release wave. While these models are capable of explaining the overall conical shape of shatter cones, they are not capable of explaining the subcone structure and the diverging and branching striations that characterize the surface of shatter cones and lead to the so-called horse-tailing effect. Here, we use the hierarchical arrangement of subcone ridges of shatter cone surfaces as key for understanding their formation. Tracing a single subcone ridge from its apex downward reveals that each ridge branches after some distance into two symmetrically equivalent subcone ridges. This pattern is repeated to form new branches. We propose that subcone ridges represent convex-curved fracture surfaces and their intersection corresponds to the bifurcation axis. The characteristic diverging striations are interpreted as the intersection lineations delimiting each subcone. Multiple symmetric crack branching is the result of rapid fracture propagation that may approach the Raleigh wave speed. We present a phenomenological model that fully constructs the shatter cone geometry to any order. The overall cone geometry including apex angle of the enveloping cone and the degree of concavity (horse-tailing) is largely governed by the convexity of the subcone ridges. Straight cones of various apical angles, constant slope, and constant bifurcation angles form if the subcone convexity is low (30°). Increasing subcone convexity leads to a stronger horse-tailing effect and the bifurcation angles increase with increasing distance from the enveloping cone apex. The model predicts possible triples of enveloping cone angle, bifurcation angle, and subcone angle. Measurements of these quantities on four shatter cones from different

Bifurcation theory for finitely smooth planar autonomous differential systems

Science.gov (United States)

Han, Maoan; Sheng, Lijuan; Zhang, Xiang

2018-03-01

In this paper we establish bifurcation theory of limit cycles for planar Ck smooth autonomous differential systems, with k ∈ N. The key point is to study the smoothness of bifurcation functions which are basic and important tool on the study of Hopf bifurcation at a fine focus or a center, and of Poincaré bifurcation in a period annulus. We especially study the smoothness of the first order Melnikov function in degenerate Hopf bifurcation at an elementary center. As we know, the smoothness problem was solved for analytic and C∞ differential systems, but it was not tackled for finitely smooth differential systems. Here, we present their optimal regularity of these bifurcation functions and their asymptotic expressions in the finite smooth case.

Discretization analysis of bifurcation based nonlinear amplifiers

Science.gov (United States)

Feldkord, Sven; Reit, Marco; Mathis, Wolfgang

2017-09-01

Recently, for modeling biological amplification processes, nonlinear amplifiers based on the supercritical Andronov-Hopf bifurcation have been widely analyzed analytically. For technical realizations, digital systems have become the most relevant systems in signal processing applications. The underlying continuous-time systems are transferred to the discrete-time domain using numerical integration methods. Within this contribution, effects on the qualitative behavior of the Andronov-Hopf bifurcation based systems concerning numerical integration methods are analyzed. It is shown exemplarily that explicit Runge-Kutta methods transform the truncated normalform equation of the Andronov-Hopf bifurcation into the normalform equation of the Neimark-Sacker bifurcation. Dependent on the order of the integration method, higher order terms are added during this transformation.A rescaled normalform equation of the Neimark-Sacker bifurcation is introduced that allows a parametric design of a discrete-time system which corresponds to the rescaled Andronov-Hopf system. This system approximates the characteristics of the rescaled Hopf-type amplifier for a large range of parameters. The natural frequency and the peak amplitude are preserved for every set of parameters. The Neimark-Sacker bifurcation based systems avoid large computational effort that would be caused by applying higher order integration methods to the continuous-time normalform equations.

Trial of self-expandable metallic stents in the palliation of tracheo ...

African Journals Online (AJOL)

Trial of self-expandable metallic stents in the palliation of tracheo-oesophageal fistula in carcinoma of the oesophagus. ... Over half of the patients in the TOF group had concomitant pneumonia at presentation with decreased survival (p = 0.010) and a hazard ratio of 10.86. Two patients died, on days 4 and 7 respectively.

Quantum entanglement and fixed-point bifurcations

International Nuclear Information System (INIS)

Hines, Andrew P.; McKenzie, Ross H.; Milburn, G.J.

2005-01-01

How does the classical phase-space structure for a composite system relate to the entanglement characteristics of the corresponding quantum system? We demonstrate how the entanglement in nonlinear bipartite systems can be associated with a fixed-point bifurcation in the classical dynamics. Using the example of coupled giant spins we show that when a fixed point undergoes a supercritical pitchfork bifurcation, the corresponding quantum state--the ground state--achieves its maximum amount of entanglement near the critical point. We conjecture that this will be a generic feature of systems whose classical limit exhibits such a bifurcation

Dedicated bifurcation stents

Directory of Open Access Journals (Sweden)

Ajith Ananthakrishna Pillai

2012-03-01

Full Text Available Bifurcation percutaneous coronary intervention (PCI is still a difficult call for the interventionist despite advancements in the instrumentation, technical skill and the imaging modalities. With major cardiac events relate to the side-branch (SB compromise, the concept and practice of dedicated bifurcation stents seems exciting. Several designs of such dedicated stents are currently undergoing trials. This novel concept and pristine technology offers new hope notwithstanding the fact that we need to go a long way in widespread acceptance and practice of these gadgets. Some of these designs even though looks enterprising, the mere complex delivering technique and the demanding knowledge of the exact coronary anatomy makes their routine use challenging.

Self-expanding metal stents in benign biliary strictures due to chronic pancreatitis

NARCIS (Netherlands)

van Berkel, A. M.; Cahen, D. L.; van Westerloo, D. J.; Rauws, E. A.; Huibregtse, K.; Bruno, M. J.

2004-01-01

Background and Study Aims: In selected patients with chronic pancreatitis in whom conventional plastic stenting fails and in whom surgery is contraindicated or declined, insertion of a biliary self-expanding metal stent (SEMS) may be a valuable treatment option. Patients and Methods: Between 1994

Use of nitinol self-expandable stents in 26 dogs with tracheal collapse.

Science.gov (United States)

Beranek, J; Jaresova, H; Rytz, U

2014-02-01

A study was designed to describe a novel approach to the treatment of tracheal collapse (TC) in dogs using self-expandable nitinol stents. Medical records were reviewed retrospectively for 26 client owned dogs in which nitinol stents were deployed. The entire length of trachea was supported independently of the extent of TC. Two overlapping stents were used instead of one in cases where one stent was not spanning the entire trachea adequately. The diameter of the cranial radiolucent portion of trachea, just behind the cricoid cartilage, was measured as a specific landmark to select the appropriate size of the stent. Two self-expandable nitinol stents were inserted in 9 of 26 dogs; the trachea in the rest of the cases was supported with only one stent. A follow up tracheoscopy was performed in 10 of 26 cases with recurrent clinical signs. Secondary tracheal stenosis in these cases was caused by stent fracture, granuloma or excessive stent shortening. Additional stents were placed successfully to expand the stenotic lumen. A support of the entire trachea may decrease risk of nitinol fracture at the end of the implant. Long term clinical improvement (25 of 26 dogs, 96 %) is comparable with the results of other studies.

Codimension-2 bifurcations of the Kaldor model of business cycle

International Nuclear Information System (INIS)

Wu, Xiaoqin P.

2011-01-01

Research highlights: → The conditions are given such that the characteristic equation may have purely imaginary roots and double zero roots. → Purely imaginary roots lead us to study Hopf and Bautin bifurcations and to calculate the first and second Lyapunov coefficients. → Double zero roots lead us to study Bogdanov-Takens (BT) bifurcation. → Bifurcation diagrams for Bautin and BT bifurcations are obtained by using the normal form theory. - Abstract: In this paper, complete analysis is presented to study codimension-2 bifurcations for the nonlinear Kaldor model of business cycle. Sufficient conditions are given for the model to demonstrate Bautin and Bogdanov-Takens (BT) bifurcations. By computing the first and second Lyapunov coefficients and performing nonlinear transformation, the normal forms are derived to obtain the bifurcation diagrams such as Hopf, homoclinic and double limit cycle bifurcations. Some examples are given to confirm the theoretical results.

Perioperative management of endovascular abdominal aortic aneurysm repair

International Nuclear Information System (INIS)

Wang Haofu; Wang Yuwei; Li Jun; Zhao Zonggang; Qi Sen

2010-01-01

Objective: To summarize the clinical experience of perioperative management in performing endovascular abdominal aortic aneurysm repair (EVAR). Methods: EVAR was performed in 22 patients with abdominal aortic aneurysm. The clinical data were retrospectively analyzed. Before treatment the functions of main organs were evaluated and certain measures were adopted in order to protect them. Useful parameters, including the length, diameter, angle and configuration of the proximal and distal aneurysmal neck, the relationship of the aneurysm to aortic branches, the distance from the lowest renal artery to the bifurcation of abdominal aorta, and the quality of access vessels (such as diameter, tortuosity and calcification degree) were determined and assessed with CTA. According to the parameters thus obtained, the suitable stent-graft with ideal diameter and length was selected, and the optimal surgery pattern was employed. Local anesthesia was employed in 20 patients, among them the local anesthesia had to be changed to general anesthesia in one. Epidural anesthesia was carried out in one patient through the surgically-reconstructed iliac artery access,and general anesthesia was employed in one patient who had Stanford type A aortic dissection. The lowest renal artery must be accurately localized before deployment of stent-graft was started. At least one patent internal iliac artery should be reserved when bilateral internal iliac arteries needed to be covered, to be covered by stages or to be reconstructed. After stent-graft placement, angiography must be performed to find out if there was any endoleak and, if any, to determine the type of endoleak and to deal with it properly. Two cases had proximal type I endoleak, so balloon dilation was employed in one and cuff implantation in another one. Distal type I endoleak occurred in one case, but, unfortunately, the iliac artery ruptured when balloon dilation was employed, therefore the patient had to receive vascular repair

Critical bifurcation surfaces of 3D discrete dynamics

Directory of Open Access Journals (Sweden)

Michael Sonis

2000-01-01

Full Text Available This paper deals with the analytical representation of bifurcations of each 3D discrete dynamics depending on the set of bifurcation parameters. The procedure of bifurcation analysis proposed in this paper represents the 3D elaboration and specification of the general algorithm of the n-dimensional linear bifurcation analysis proposed by the author earlier. It is proven that 3D domain of asymptotic stability (attraction of the fixed point for a given 3D discrete dynamics is bounded by three critical bifurcation surfaces: the divergence, flip and flutter surfaces. The analytical construction of these surfaces is achieved with the help of classical Routh–Hurvitz conditions of asymptotic stability. As an application the adjustment process proposed by T. Puu for the Cournot oligopoly model is considered in detail.

Mechanical Recanalization of Cerebral Artery Embolic Occlusion Using a Self-Expanding Stent: Experimental Analysis in Canine Model

International Nuclear Information System (INIS)

Choi, Jin Woo; Kim, Snag Joon; Lee, Deok Hee; Suh, Dae Chul

2011-01-01

To evaluate the feasibility of a self-expanding stent for acute embolic occlusion, and recanalization mechanism by histologic examination. Five mongrel dogs were used as study subjects. Each vertebral artery was occluded, and a self-expanding stent was used for recanalization. We evaluated the technical success rate for the placement of the stent to the targeted vessel, the recanalization rate, and residual stenosis. We obtained two specimens of the stented vertebral arteries for histologic evaluation. One dog died of an unknown cause during the induction of anesthesia. In two dogs, only one side of the vertebral artery was used, whereas both vertebral arteries were used in the remaining dogs. A total of six vertebral arteries were successfully occluded. The technical success rate for stenting without complication was 66.7%. The immediate recanalization rate after stenting was 100%. The residual stenosis was 35.6 ± 18.6%. On microscopic examination, the stent concentrically displaced the clot and the clot was captured between the stent mesh and arterial wall. Self-expanding stents were effective in revascularizing the cerebrovascular embolic occlusion. The self-expanding stent seemed to achieve recanalization by pushing the clot to the arterial wall and capturing the clot between the stent mesh and arterial wall.

Mechanical Recanalization of Cerebral Artery Embolic Occlusion Using a Self-Expanding Stent: Experimental Analysis in Canine Model

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Choi, Jin Woo; Kim, Snag Joon; Lee, Deok Hee; Suh, Dae Chul [Dept. of Radiology and Research Institute of Radiology, Asan Medical Center, Ulsan University College of Medicine, Seoul (Korea, Republic of)

2011-07-15

To evaluate the feasibility of a self-expanding stent for acute embolic occlusion, and recanalization mechanism by histologic examination. Five mongrel dogs were used as study subjects. Each vertebral artery was occluded, and a self-expanding stent was used for recanalization. We evaluated the technical success rate for the placement of the stent to the targeted vessel, the recanalization rate, and residual stenosis. We obtained two specimens of the stented vertebral arteries for histologic evaluation. One dog died of an unknown cause during the induction of anesthesia. In two dogs, only one side of the vertebral artery was used, whereas both vertebral arteries were used in the remaining dogs. A total of six vertebral arteries were successfully occluded. The technical success rate for stenting without complication was 66.7%. The immediate recanalization rate after stenting was 100%. The residual stenosis was 35.6 {+-} 18.6%. On microscopic examination, the stent concentrically displaced the clot and the clot was captured between the stent mesh and arterial wall. Self-expanding stents were effective in revascularizing the cerebrovascular embolic occlusion. The self-expanding stent seemed to achieve recanalization by pushing the clot to the arterial wall and capturing the clot between the stent mesh and arterial wall.

Reinforced aortic root reconstruction for acute type A aortic dissection involving the aortic root

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Han Qing-qi

2013-06-01

Full Text Available OBJECTIVE: There are debates regarding the optimal approach for AAAD involving the aortic root. We described a modified reinforced aortic root reconstruction approach for treating AAAD involving the aortic root. METHODS: A total of 161 patients with AAAD involving the aortic root were treated by our modified reinforced aortic root reconstruction approach from January 1998 to December 2008. Key features of our modified approach were placement of an autologous pericardial patch in the false lumen, lining of the sinotubular junction lumen with a polyester vascular ring, and wrapping of the vessel with Teflon strips. Outcome measures included post-operative mortality, survival, complications, and level of aortic regurgitation. RESULTS: A total of 161 patients were included in the study (mean age: 43.3 1 15.5 years. The mean duration of follow-up was 5.1 1 2.96 years (2-12 years. A total of 10 (6.2% and 11 (6.8% patients died during hospitalization and during follow-up, respectively. Thirty-one (19.3% patients experienced postoperative complications. The 1-, 3-, 5-, and 10-year survival rates were 99.3%, 98%, 93.8%, and 75.5%, respectively. There were no instances of recurrent aortic dissection, aortic aneurysm, or pseudoaneurysm during the entire study period. The severity of aortic regurgitation dramatically decreased immediately after surgery (from 28.6% to 0% grade 3-4 and thereafter slightly increased (from 0% to 7.2% at 5 years and 9.1% at 10 years. CONCLUSION: This modified reinforced aortic root reconstruction was feasible, safe and durable/effective, as indicated by its low mortality, low postoperative complications and high survival rate.

Implantation of modified Y-shaped self-expandable stent for the treatment of stenosis of gastroenteric stoma: preliminary results in five cases

International Nuclear Information System (INIS)

Wu Gang; Si Jiangtao; Han Xinwei; Jiao Dechao; Ding Pengxu; Fu Mingti; Li Zhen; Ma Ji

2010-01-01

Objective To investigate the feasibility and therapeutic effect of stenting therapy by using modified Y-shaped self-expandable metal stent for the stenosis of gastroenteric stoma. Methods: According to the particular anatomic structures and the pathological features of the narrowed gastroenteric stoma,the authors designed a modified Y-shaped self-expandable metal stent. Under the fluoroscopic guidance, implantation of modified Y-shaped self-expandable metal stent was performed in 5 patients with narrowed gastroenteric stoma. The technical safety and the clinical results were evaluated. Results: The modified Y-shaped self-expandable metal stent was successfully implanted with one procedure in all five patients. After the implantation the symptoms such as nausea, vomiting, abdominal distension were promptly relieved, and the patients' living quality was markedly improved. Conclusion: The stenting therapy with modified Y-shaped self-expandable metal stent can rapidly relieve the stenosis of gastroenteric stoma once for all. The technique is feasible and the short-term effect is reliable, therefore, it is worth popularizing this therapy in clinical practice. (authors)

Resonant Homoclinic Flips Bifurcation in Principal Eigendirections

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Tiansi Zhang

2013-01-01

Full Text Available A codimension-4 homoclinic bifurcation with one orbit flip and one inclination flip at principal eigenvalue direction resonance is considered. By introducing a local active coordinate system in some small neighborhood of homoclinic orbit, we get the Poincaré return map and the bifurcation equation. A detailed investigation produces the number and the existence of 1-homoclinic orbit, 1-periodic orbit, and double 1-periodic orbits. We also locate their bifurcation surfaces in certain regions.

Use of retrievable self-expanding stent in treating childhood benign oesophageal stricture

International Nuclear Information System (INIS)

Yu Juming; Fan Guoping; Zhong Weixing; Zhu Ming

2007-01-01

Objective: To evaluate the methods and effect of retrievable self-expanding esophageal stent in treating benign esophageal stenosis of children. Methods: The covered retrievable expandable nitinol stents were placed in 10 children with corrosive esophageal stenosis and post-anastomotic stenosis, age ranged from 2 to 12 years, the dysphagia scores were 3, Barium esophagography was taken before the use of retrievable stent. Results: The stents were placed safely in all patients without complications and were successfully removed after all. After the stent placement, all patients could take solid food without dysphagia. During 6 to 12 months follow-up after the stent removal, all children could eat satisfactorily with the dysphagia score as 0. Conclusion: The use of covered retrievable expandable stent is effective and safe in treating childhood benign esophageal stenosis. (authors)

Three-year hemodynamic performance, left ventricular mass regression, and prosthetic-patient mismatch after rapid deployment aortic valve replacement in 287 patients.

Science.gov (United States)

Haverich, Axel; Wahlers, Thorsten C; Borger, Michael A; Shrestha, Malakh; Kocher, Alfred A; Walther, Thomas; Roth, Matthias; Misfeld, Martin; Mohr, Friedrich W; Kempfert, Joerg; Dohmen, Pascal M; Schmitz, Christoph; Rahmanian, Parwis; Wiedemann, Dominik; Duhay, Francis G; Laufer, Günther

2014-12-01

Superior aortic valve hemodynamic performance can accelerate left ventricular mass regression and enhance survival and functional status after surgical aortic valve replacement. This can be achieved by rapid deployment aortic valve replacement using a subannular balloon-expandable stent frame, which functionally widens and reshapes the left ventricular outflow tract, to ensure a larger effective orifice area compared with conventional surgical valves. We report the intermediate-term follow-up data from a large series of patients enrolled in the Surgical Treatment of Aortic Stenosis With a Next Generation Surgical Aortic Valve (TRITON) trial. In a prospective, multicenter (6 European hospitals), single-arm study, 287 patients with aortic stenosis underwent rapid deployment aortic valve replacement using a stented trileaflet bovine pericardial bioprosthesis. Core laboratory echocardiography was performed at baseline, discharge, and 3 months, 1 year, and 3 years after rapid deployment aortic valve replacement. The mean patient age was 75.7 ± 6.7 years (range, 45-93; 49.1% women). The mean aortic valve gradient significantly decreased from discharge to 3 years of follow-up. The mean effective orifice area remained stable from discharge to 3 years. At 1 year, the left ventricular mass index had decreased by 14% (P replacement using a subannular balloon-expandable stent frame demonstrated excellent hemodynamic performance and significant left ventricular mass regression. With continued follow-up, future studies will establish whether these favorable structural changes correlate with improvement in long-term survival and functional status. Copyright © 2014 The American Association for Thoracic Surgery. Published by Elsevier Inc. All rights reserved.

Bifurcation analysis of a three dimensional system

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Yongwen WANG

2018-04-01

Full Text Available In order to enrich the stability and bifurcation theory of the three dimensional chaotic systems, taking a quadratic truncate unfolding system with the triple singularity equilibrium as the research subject, the existence of the equilibrium, the stability and the bifurcation of the system near the equilibrium under different parametric conditions are studied. Using the method of mathematical analysis, the existence of the real roots of the corresponding characteristic equation under the different parametric conditions is analyzed, and the local manifolds of the equilibrium are gotten, then the possible bifurcations are guessed. The parametric conditions under which the equilibrium is saddle-focus are analyzed carefully by the Cardan formula. Moreover, the conditions of codimension-one Hopf bifucation and the prerequisites of the supercritical and subcritical Hopf bifurcation are found by computation. The results show that the system has abundant stability and bifurcation, and can also supply theorical support for the proof of the existence of the homoclinic or heteroclinic loop connecting saddle-focus and the Silnikov's chaos. This method can be extended to study the other higher nonlinear systems.

MMP-2 Isoforms in Aortic Tissue and Serum of Patients with Ascending Aortic Aneurysms and Aortic Root Aneurysms

Science.gov (United States)

Tscheuschler, Anke; Meffert, Philipp; Beyersdorf, Friedhelm; Heilmann, Claudia; Kocher, Nadja; Uffelmann, Xenia; Discher, Philipp; Siepe, Matthias; Kari, Fabian A.

2016-01-01

Objective The need for biological markers of aortic wall stress and risk of rupture or dissection of ascending aortic aneurysms is obvious. To date, wall stress cannot be related to a certain biological marker. We analyzed aortic tissue and serum for the presence of different MMP-2 isoforms to find a connection between serum and tissue MMP-2 and to evaluate the potential of different MMP-2 isoforms as markers of high wall stress. Methods Serum and aortic tissue from n = 24 patients and serum from n = 19 healthy controls was analyzed by ELISA and gelatin zymography. 24 patients had ascending aortic aneurysms, 10 of them also had aortic root aneurysms. Three patients had normally functioning valves, 12 had regurgitation alone, eight had regurgitation and stenosis and one had only stenosis. Patients had bicuspid and tricuspid aortic valves (9/15). Serum samples were taken preoperatively, and the aortic wall specimen collected during surgical aortic repair. Results Pro-MMP-2 was identified in all serum and tissue samples. Pro-MMP-2 was detected in all tissue and serum samples from patients with ascending aortic/aortic root aneurysms, irrespective of valve morphology or other clinical parameters and in serum from healthy controls. We also identified active MMP-2 in all tissue samples from patients with ascending aortic/aortic root aneurysms. None of the analyzed serum samples revealed signals relatable to active MMP-2. No correlation between aortic tissue total MMP-2 or tissue pro-MMP-2 or tissue active MMP-2 and serum MMP-2 was found and tissue MMP-2/pro-MMP-2/active MMP-2 did not correlate with aortic diameter. This evidence shows that pro-MMP-2 is the predominant MMP-2 species in serum of patients and healthy individuals and in aneurysmatic aortic tissue, irrespective of aortic valve configuration. Active MMP-2 species are either not released into systemic circulation or not detectable in serum. There is no reliable connection between aortic tissue—and serum MMP-2

Results of the new nitinol self-expandable stents for distal biliary structures

NARCIS (Netherlands)

Smits, M.; Huibregtse, K.; Tytgat, G.

1995-01-01

The nitinol stent is a self-expandable spiral stent made of nickel-titanium alloy. We performed a pilot study to evaluate the method of stent insertion and stent efficacy. Twenty-eight patients with irresectable malignancy had nitinol stents inserted for obstructive jaundice due to distal biliary

Self-expanding intracoronary stents in the treatment of coronary artery disease: new developments and future directions

NARCIS (Netherlands)

Lu, H.; Grundeken, M. J.; Koch, K. T.; Wykrzykowska, J. J.

2013-01-01

The first stent implanted in the human coronary circulation was a self-expandable (SE) stent and was introduced almost simultaneously with the first balloon-expandable (BE) stents in the late 1980s. Nowadays, the majority of the available stents are delivered by balloon expansion. While BE stents

Malignant Gastroduodenal Obstruction: Treatment with Self-Expanding Uncovered Wallstent

International Nuclear Information System (INIS)

Gutzeit, Andreas; Binkert, Christoph A.; Schoch, Eric; Sautter, Thomas; Jost, Res; Zollikofer, Christoph L.

2009-01-01

Purpose: To retrospectively evaluate the clinical effectiveness of a self-expanding uncovered Wallstent in patients with malignant gastroduodenal obstruction. Materials and Methods: Under combined endoscopic and fluoroscopic guidance, 29 patients with a malignant gastroduodenal stenosis were treated with a self-expanding uncovered metallic Wallstent. A dysphagia score was assessed before and after the intervention to measure the success of this palliative therapy. The dysphagia score ranged between grade 0 to grade 4: grade 0 = able to tolerate solid food, grade 1 = able to tolerate soft food, grade 2 = able to tolerate thick liquids, grade 3 = able to tolerate water or clear fluids, and grade 4 = unable to tolerate anything perorally. Stent patency and patients survival rates were calculated. Results: The insertion of the gastroduodenal stent was technically successful in 28 patients (96.5%). After stenting, 25 patients (86.2%) showed clinical improvement by at least one score point. During follow-up, 22 (78.5%) of 28 patients showed no stent occlusion until death and did not have to undergo any further intervention. In six patients (20.6%), all of whom were treated with secondary stent insertions, occlusion with tumor ingrowth and/or overgrowth was observed after the intervention. The median period of primary stent patency in our study was 240 days. Conclusion: Placement of an uncovered Wallstent is clinically effective in patients with malignant gastroduodenal obstruction. Stent placement is associated with high technical success, good palliation effect, and high durability of stent function.

Transcatheter Aortic Valve Replacement in Bicuspid Aortic Valve Disease

DEFF Research Database (Denmark)

Mylotte, Darren; Lefevre, Thierry; Søndergaard, Lars

2014-01-01

(16.7% balloon-expandable THV vs. 17.6% self-expandable THV, p = 0.99). MSCT sizing was associated with reduced AR on multivariate analysis (odds ratio [OR]: 0.19, 95% confidence intervals [CI]: 0.08 to 0.45; p day device safety, success, and efficacy were noted in 79.1%, 89...

Stone extraction balloon-guided repeat self-expanding metal stent placement

Institute of Scientific and Technical Information of China (English)

Hyung; Hun; Kim; Jeong; Seop; Moon; Soo; Hyung; Ryu; Jung; Hwan; Lee; You; Sun; Kim

2010-01-01

Self-expanding metal stent (SEMS) placement offers safe and effective palliation in patients with upper gastrointestinal obstruction due to a malignancy. Well described complications of SEMS placement include tumor growth, obstruction, and stent migration. SEMS occlusions are treated by SEMS redeployment, argon plasma coagulation application, balloon dilation, and surgical bypass. At our center, we usually place the second SEMS into the first SEMS if there is complete occlusion by the tumor. We discovered a...

Results of aortic root reimplantation in patients with ascending aortic aneurysm and concomitant aortic insufficiency

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А. М. Чернявский

2016-01-01

Full Text Available Objective. The research was designed to evaluate the results of valve-sparing operations: aortic root reimplantation versus aortic valve reimplantation when repairing an ascending aortic aneurysm with concomitant aortic insufficiency.Methods. Within a blind prospective randomized study conducted over a period from 2011 to 2015, 64 patients underwent aortic valve-sparing surgery. The inclusion criteria were the presence of an aortic aneurysm of the ascending aorta exceeding 4.5 cm and concomitant aortic insufficiency. All patients were divided into two groups: FS-group, aortic root reimplantation (modified Florida Sleeve technique (n = 32 and D-group, aortic valve reimplantation (David procedure (n = 32. The average age of patients was 57±13 (23–73 years in the FS-group and 55±11 (15–72 years in the D-group (p = 0.54. Both groups had 78% of males (p>0.99. A Marfan syndrome was identified in 6% and 9% in the FS-group and D-group respectively (p>0.99. Mean diameter of the sinuses of Valsalva was 51±7 mm and 56±10 mm (p = 0.09, aortic insufficiency 2.6±0.7 and 2.8±0.8 (p = 0.15 in the FS-group and D-group respectively. In the FS-group and D-group LVEDD amounted to 5.5±0.7 mm and 5.9±1.0 mm (p = 0.09 respectively. All patients took echocardiography in the preoperative, postoperative and follow-up periods.Results. In the long-term period, the degree of aortic regurgitation was 1.2±0.1 in the FS-group and 1.3±0.6 in the D-group (p = 0.72. LVEDD was 123±23 mm in the FS-group and 139.6±80 mm in the D-group at follow-up (p = 0.77. There were no statistically significant differences in the analysis of complications. Overall 30-day in-hospital mortality was 7.8%. There were 2 (6.3% deaths in the FS-group and 3 (9.4% in the D-group (p = 0.5.Late mortality was 6.3% in the FS-group and 3.1% in the D-group (p>0.99. Cumulative survival at 4 years was 84.3% and 84.8% in the FS-group and the D-group respectively (p = 0.94. Cumulative freedom from

Endovascular Treatment of Infrarenal Abdominal Aortic Aneurysm with Short and Angulated Neck in High-Risk Patient

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Stylianos Koutsias

2013-01-01

Full Text Available Endovascular treatment of abdominal aortic aneurysms (AAA is an established alternative to open repair. However lifelong surveillance is still required to monitor endograft function and signal the need for secondary interventions (Hobo and Buth 2006. Aortic morphology, especially related to the proximal neck, often complicates the procedure or increases the risk for late device-related complications (Hobo et al. 2007 and Chisci et al. 2009. The definition of a short and angulated neck is based on length (60° (Hobo et al. 2007 and Chisci et al. 2009. A challenging neck also offers difficulties during open repairs (OR, necessitating extensive dissection with juxta- or suprarenal aortic cross-clamping. Patients with extensive aneurysmal disease typically have more comorbidities and may not tolerate extensive surgical trauma (Sarac et al. 2002. It is, therefore, unclear whether aneurysms with a challenging proximal neck should be offered EVAR or OR (Cox et al. 2006, Choke et al. 2006, Robbins et al. 2005, Sternbergh III et al. 2002, Dillavou et al. 2003, and Greenberg et al. 2003. In our case the insertion of a thoracic endograft followed by the placement of a bifurcated aortic endograft for the treatment of a very short and severely angulated neck proved to be feasible offering acceptable duration of aneurysm exclusion. This adds up to our armamentarium in the treatment of high-risk patients, and it should be considered in emergency cases when the fenestrated and branched endografts are not available.

Hemodialysis shunts-related subclavian vein stenosis : treatment with self-expandable metallic stent

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Kim, Sang Gyee; Lee, Young Chul; Shin, Sang Soo; Kim, Yun Hyeon; Kim, Jae Kyu; Kang, Heoung Keun; Jeong, Sang Young; Choi, Su Jin Na [Chonnam Univ. College of Medicine, Kwangju (Korea, Republic of)

1999-04-01

To evaluate the usefulness of placement of self-expandable stents in hemodialytic shunt-related subclavian vein stenosis. Self-expandable metallic stent was placed in nine patients with hemodialytic shunt-related subclavian vein stenosis. In seven cases, angioplasty was attempted before stent placement; in five, stents were placed immediately after failed angioplasty; and in two, due to restenosis after angioplasty. Procedures involved a 10mm diameter, 7-10cm length Wallstent in eight cases, and a 10mm diameter, 8cm length Hanaro stent in one. In all cases, clinical follow-up, which included physical examination and the measurement of venous resistance pressure during hemodialysis, was performed. The follow-up period was between 5 months and 1 year 7 months. Repeated intervention was performed if restenosis was detected. The stenotic sites were in eight cases the site of a previous subclavian venous line, and in one, the site of anatomic narrowing at the thoracic inlet of the subclavian vein. The technical success rate was 100%;a resulting complication was stent migration into the right atrium in one case in which a Hanaro stent had been used; this was removed by snaring. During follow-up of the eight patients in whon stent placement was successful, restenosis developed in three cases. This occurred during the 7th, 8th, and 15th month, respectively. Two such cases were treated by balloon dilatation. In hemodialytic shunt-related subclavian vein stenosis, treatment involving the use of a self-expandable metallic stent is useful, especially for treating a lesion which has not responded to angioplasty with a high patency rate.

Hemodialysis shunts-related subclavian vein stenosis : treatment with self-expandable metallic stent

International Nuclear Information System (INIS)

Kim, Sang Gyee; Lee, Young Chul; Shin, Sang Soo; Kim, Yun Hyeon; Kim, Jae Kyu; Kang, Heoung Keun; Jeong, Sang Young; Choi, Su Jin Na

1999-01-01

To evaluate the usefulness of placement of self-expandable stents in hemodialytic shunt-related subclavian vein stenosis. Self-expandable metallic stent was placed in nine patients with hemodialytic shunt-related subclavian vein stenosis. In seven cases, angioplasty was attempted before stent placement; in five, stents were placed immediately after failed angioplasty; and in two, due to restenosis after angioplasty. Procedures involved a 10mm diameter, 7-10cm length Wallstent in eight cases, and a 10mm diameter, 8cm length Hanaro stent in one. In all cases, clinical follow-up, which included physical examination and the measurement of venous resistance pressure during hemodialysis, was performed. The follow-up period was between 5 months and 1 year 7 months. Repeated intervention was performed if restenosis was detected. The stenotic sites were in eight cases the site of a previous subclavian venous line, and in one, the site of anatomic narrowing at the thoracic inlet of the subclavian vein. The technical success rate was 100%;a resulting complication was stent migration into the right atrium in one case in which a Hanaro stent had been used; this was removed by snaring. During follow-up of the eight patients in whon stent placement was successful, restenosis developed in three cases. This occurred during the 7th, 8th, and 15th month, respectively. Two such cases were treated by balloon dilatation. In hemodialytic shunt-related subclavian vein stenosis, treatment involving the use of a self-expandable metallic stent is useful, especially for treating a lesion which has not responded to angioplasty with a high patency rate

Local bifurcation analysis in nuclear reactor dynamics by Sotomayor’s theorem

International Nuclear Information System (INIS)

Pirayesh, Behnam; Pazirandeh, Ali; Akbari, Monireh

2016-01-01

Highlights: • When the feedback reactivity is considered as a nonlinear function some complex behaviors may emerge in the system such as local bifurcation phenomenon. • The qualitative behaviors of a typical nuclear reactor near its equilibrium points have been studied analytically. • Comprehensive analytical bifurcation analyses presented in this paper are transcritical bifurcation, saddle- node bifurcation and pitchfork bifurcation. - Abstract: In this paper, a qualitative approach has been used to explore nuclear reactor behaviors with nonlinear feedback. First, a system of four dimensional ordinary differential equations governing the dynamics of a typical nuclear reactor is introduced. These four state variables are the relative power of the reactor, the relative concentration of delayed neutron precursors, the fuel temperature and the coolant temperature. Then, the qualitative behaviors of the dynamical system near its equilibria have been studied analytically by using local bifurcation theory and Sotomayor’s theorem. The results indicated that despite the uncertainty of the reactivity, we can analyze the qualitative behavior changes of the reactor from the bifurcation point of view. Notably, local bifurcations that were considered in this paper include transcritical bifurcation, saddle-node bifurcation and pitchfork bifurcation. The theoretical analysis showed that these three types of local bifurcations may occur in the four dimensional dynamical system. In addition, to confirm the analytical results the numerical simulations are given.

Global Bifurcation of a Novel Computer Virus Propagation Model

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Jianguo Ren

2014-01-01

Full Text Available In a recent paper by J. Ren et al. (2012, a novel computer virus propagation model under the effect of the antivirus ability in a real network is established. The analysis there only partially uncovers the dynamics behaviors of virus spread over the network in the case where around bifurcation is local. In the present paper, by mathematical analysis, it is further shown that, under appropriate parameter values, the model may undergo a global B-T bifurcation, and the curves of saddle-node bifurcation, Hopf bifurcation, and homoclinic bifurcation are obtained to illustrate the qualitative behaviors of virus propagation. On this basis, a collection of policies is recommended to prohibit the virus prevalence. To our knowledge, this is the first time the global bifurcation has been explored for the computer virus propagation. Theoretical results and corresponding suggestions may help us suppress or eliminate virus propagation in the network.

Fully Covered Self-Expandable Metal Stents for Treatment of Both Benign and Malignant Biliary Disorders

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Ahmed Abdel Samie

2012-01-01

Full Text Available Transpapillary stents are increasingly being used for biliary strictures, whether benign or malignant. However, there are different stent types and available data is controversial. Recently, completely covered self-expandable metal stents (CSEMSs have been proposed as an alternative therapeutic option in different biliary indications, including strictures of the distal bile duct, anastomotic stenosis after orthotopic liver transplantation, bile duct leaks, periampullary perforation following endoscopic sphincterotomy (ES, and postsphincterotomy bleeding. Despite the higher costs of these devices, fully covered self-expanding metal stents seem to be a suitable therapeutic option to relief biliary obstruction due to bile duct stenosis, regardless of the underlying cause.

Fully Covered Self-Expandable Metal Stents for Treatment of Both Benign and Malignant Biliary Disorders

Science.gov (United States)

Abdel Samie, Ahmed; Theilmann, Lorenz

2012-01-01

Transpapillary stents are increasingly being used for biliary strictures, whether benign or malignant. However, there are different stent types and available data is controversial. Recently, completely covered self-expandable metal stents (CSEMSs) have been proposed as an alternative therapeutic option in different biliary indications, including strictures of the distal bile duct, anastomotic stenosis after orthotopic liver transplantation, bile duct leaks, periampullary perforation following endoscopic sphincterotomy (ES), and postsphincterotomy bleeding. Despite the higher costs of these devices, fully covered self-expanding metal stents seem to be a suitable therapeutic option to relief biliary obstruction due to bile duct stenosis, regardless of the underlying cause. PMID:22761543

Decreased expression of fibulin-4 in aortic wall of aortic dissection.

Science.gov (United States)

Huawei, P; Qian, C; Chuan, T; Lei, L; Laing, W; Wenlong, X; Wenzhi, L

2014-02-01

In this research, we will examine the expression of Fibulin-4 in aortic wall to find out its role in aortic dissection development. The samples of aortic wall were obtained from 10 patients operated for acute ascending aortic dissection and five patients for chronic ascending aortic dissection. Another 15 pieces of samples from patients who had coronary artery bypass were as controls. The aortic samples were stained with aldehyde magenta dyeing to evaluate the arrangement of elastic fibers. The Fibulin-4 protein and mRNA expression were both determined by Western blot and realtime quantitative polymerase chain reaction. Compared with the control group, both in acute and chronic ascending aortic dissection, elastic fiber fragments increased and the expression of fibulin-4 protein significantly decreased (P= 0.045 < 0.05). The level of fibulin-4 mRNA decreased in acute ascending aortic dissection (P= 0.034 < 0.05), while it increased in chronic ascending aortic dissection (P=0.004 < 0.05). The increased amounts of elastic fiber fragments were negatively correlated with the expression of fibulin-4 mRNA in acute ascending aortic dissection. In conclusion, in aortic wall of ascending aortic dissection, the expression of fibulin-4 protein decreased and the expression of fibulin-4 mRNA was abnormal. Fibulin-4 may play an important role in the pathogenesis of aortic dissection.

Reoperative Aortic Root Replacement in Patients with Previous Aortic Root or Aortic Valve Procedures

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Byung Kwon Chong

2016-08-01

Full Text Available Background: Generalization of standardized surgical techniques to treat aortic valve (AV and aortic root diseases has benefited large numbers of patients. As a consequence of the proliferation of patients receiving aortic root surgeries, surgeons are more frequently challenged by reoperative aortic root procedures. The aim of this study was to evaluate the outcomes of redo-aortic root replacement (ARR. Methods: We retrospectively reviewed 66 patients (36 male; mean age, 44.5±9.5 years who underwent redo-ARR following AV or aortic root procedures between April 1995 and June 2015. Results: Emergency surgeries comprised 43.9% (n=29. Indications for the redo-ARR were aneurysm (n=12, pseudoaneurysm (n=1, or dissection (n=6 of the residual native aortic sinus in 19 patients (28.8%, native AV dysfunction in 8 patients (12.1%, structural dysfunction of an implanted bioprosthetic AV in 19 patients (28.8%, and infection of previously replaced AV or proximal aortic grafts in 30 patients (45.5%. There were 3 early deaths (4.5%. During follow- up (median, 54.65 months; quartile 1–3, 17.93 to 95.71 months, there were 14 late deaths (21.2%, and 9 valve-related complications including reoperation of the aortic root in 1 patient, infective endocarditis in 3 patients, and hemorrhagic events in 5 patients. Overall survival and event-free survival rates at 5 years were 81.5%±5.1% and 76.4%±5.4%, respectively. Conclusion: Despite technical challenges and a high rate of emergency conditions in patients requiring redo-ARR, early and late outcomes were acceptable in these patients.

Self-expandable metal stent placement versus emergency resection for malignant proximal colon obstructions

NARCIS (Netherlands)

Amelung, F.J.; Draaisma, W.A.; Consten, E.C.; Siersema, P.D.; Borg, F. ter

2017-01-01

BACKGROUND: Traditionally, all patients with a malignant obstruction of the proximal colon (MOPC) are treated with emergency resection. However, recent data suggest that Self-expandable metallic stent (SEMS) placement could lower mortality and morbidity rates. This study therefore aimed to compare

Wall stress on ascending thoracic aortic aneurysms with bicuspid compared with tricuspid aortic valve.

Science.gov (United States)

Xuan, Yue; Wang, Zhongjie; Liu, Raymond; Haraldsson, Henrik; Hope, Michael D; Saloner, David A; Guccione, Julius M; Ge, Liang; Tseng, Elaine

2018-03-08

Guidelines for repair of bicuspid aortic valve-associated ascending thoracic aortic aneurysms have been changing, most recently to the same criteria as tricuspid aortic valve-ascending thoracic aortic aneurysms. Rupture/dissection occurs when wall stress exceeds wall strength. Recent studies suggest similar strength of bicuspid aortic valve versus tricuspid aortic valve-ascending thoracic aortic aneurysms; thus, comparative wall stress may better predict dissection in bicuspid aortic valve versus tricuspid aortic valve-ascending thoracic aortic aneurysms. Our aim was to determine whether bicuspid aortic valve-ascending thoracic aortic aneurysms had higher wall stresses than their tricuspid aortic valve counterparts. Patients with bicuspid aortic valve- and tricuspid aortic valve-ascending thoracic aortic aneurysms (bicuspid aortic valve = 17, tricuspid aortic valve = 19) greater than 4.5 cm underwent electrocardiogram-gated computed tomography angiography. Patient-specific 3-dimensional geometry was reconstructed and loaded to systemic pressure after accounting for prestress geometry. Finite element analyses were performed using the LS-DYNA solver (LSTC Inc, Livermore, Calif) with user-defined fiber-embedded material model to determine ascending thoracic aortic aneurysm wall stress. Bicuspid aortic valve-ascending thoracic aortic aneurysms 99th-percentile longitudinal stresses were 280 kPa versus 242 kPa (P = .028) for tricuspid aortic valve-ascending thoracic aortic aneurysms in systole. These stresses did not correlate to diameter for bicuspid aortic valve-ascending thoracic aortic aneurysms (r = -0.004) but had better correlation to tricuspid aortic valve-ascending thoracic aortic aneurysms diameter (r = 0.677). Longitudinal stresses on sinotubular junction were significantly higher in bicuspid aortic valve-ascending thoracic aortic aneurysms than in tricuspid aortic valve-ascending thoracic aortic aneurysms (405 vs 329 kPa, P = .023). Bicuspid

Bifurcation and instability problems in vortex wakes

DEFF Research Database (Denmark)

Aref, Hassan; Brøns, Morten; Stremler, Mark A.

2007-01-01

A number of instability and bifurcation problems related to the dynamics of vortex wake flows are addressed using various analytical tools and approaches. We discuss the bifurcations of the streamline pattern behind a bluff body as a vortex wake is produced, a theory of the universal Strouhal......-Reynolds number relation for vortex wakes, the bifurcation diagram for "exotic" wake patterns behind an oscillating cylinder first determined experimentally by Williamson & Roshko, and the bifurcations in topology of the streamlines pattern in point vortex streets. The Hamiltonian dynamics of point vortices...... in a periodic strip is considered. The classical results of von Kármán concerning the structure of the vortex street follow from the two-vortices-in-a-strip problem, while the stability results follow largely from a four-vortices-in-a-strip analysis. The three-vortices-in-a-strip problem is argued...

Aortic Annular Enlargement during Aortic Valve Replacement

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Selman Dumani

2016-09-01

Full Text Available In the surgery of aortic valve replacement is always attempted, as much as possible, to implant the larger prosthesis with the mains goals to enhance the potential benefits, to minimise transvalvular gradient, decrease left ventricular size and avoid the phenomenon of patient-prosthesis mismatch. Implantation of an ideal prosthesis often it is not possible, due to a small aortic annulus. A variety of aortic annulus enlargement techniques is reported to avoid patient-prosthesis mismatch. We present the case that has submitted four three times open heart surgery. We used Manouguian technique to enlarge aortic anulus with excellent results during the fourth time of surgery.

Hopf bifurcation analysis of Chen circuit with direct time delay feedback

International Nuclear Information System (INIS)

Hai-Peng, Ren; Wen-Chao, Li; Ding, Liu

2010-01-01

Direct time delay feedback can make non-chaotic Chen circuit chaotic. The chaotic Chen circuit with direct time delay feedback possesses rich and complex dynamical behaviours. To reach a deep and clear understanding of the dynamics of such circuits described by delay differential equations, Hopf bifurcation in the circuit is analysed using the Hopf bifurcation theory and the central manifold theorem in this paper. Bifurcation points and bifurcation directions are derived in detail, which prove to be consistent with the previous bifurcation diagram. Numerical simulations and experimental results are given to verify the theoretical analysis. Hopf bifurcation analysis can explain and predict the periodical orbit (oscillation) in Chen circuit with direct time delay feedback. Bifurcation boundaries are derived using the Hopf bifurcation analysis, which will be helpful for determining the parameters in the stabilisation of the originally chaotic circuit

Identification of neural firing patterns, frequency and temporal coding mechanisms in individual aortic baroreceptors

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Huaguang eGu

2015-08-01

Full Text Available In rabbit depressor nerve fibers, an on-off firing pattern, period-1 firing, and integer multiple firing with quiescent state were observed as the static pressure level was increased. A bursting pattern with bursts at the systolic phase of blood pressure, continuous firing, and bursting with burst at diastolic phase and quiescent state at systolic phase were observed as the mean level of the dynamic blood pressure was increased. For both static and dynamic pressures, the firing frequency of the first two firing patterns increased and of the last firing pattern decreased due to the quiescent state. If the quiescent state is disregarded, the spike frequency becomes an increasing trend. The instantaneous spike frequency of the systolic phase bursting, continuous firing, and diastolic phase bursting can reflect the temporal process of the systolic phase, whole procedure, and diastolic phase of the dynamic blood pressure signal, respectively. With increasing the static current corresponding to pressure level, the deterministic Hodgkin-Huxley (HH model manifests a process from a resting state first to period-1 firing via a subcritical Hopf bifurcation and then to a resting state via a supercritical Hopf bifurcation, and the firing frequency increases. The on-off firing and integer multiple firing were here identified as noise-induced firing patterns near the subcritical and supercritical Hopf bifurcation points, respectively, using the stochastic HH model. The systolic phase bursting and diastolic phase bursting were identified as pressure-induced firings near the subcritical and supercritical Hopf bifurcation points, respectively, using an HH model with a dynamic signal. The firing, spike frequency, and instantaneous spike frequency observed in the experiment were simulated and explained using HH models. The results illustrate the dynamics of different firing patterns and the frequency and temporal coding mechanisms of aortic baroreceptor.

A codimension two bifurcation in a railway bogie system

DEFF Research Database (Denmark)

Zhang, Tingting; True, Hans; Dai, Huanyun

2017-01-01

In this paper, a comprehensive analysis is presented to investigate a codimension two bifurcation that exists in a nonlinear railway bogie dynamic system combining theoretical analysis with numerical investigation. By using the running velocity V and the primary longitudinal stiffness (Formula...... coexist in a range of the bifurcation parameters which can lead to jumps in the lateral oscillation amplitude of the railway bogie system. Furthermore, reduce the values of the bifurcation parameters gradually. Firstly, the supercritical Hopf bifurcation turns into a subcritical one with multiple limit...

Hopf Bifurcation of Compound Stochastic van der Pol System

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Shaojuan Ma

2016-01-01

Full Text Available Hopf bifurcation analysis for compound stochastic van der Pol system with a bound random parameter and Gaussian white noise is investigated in this paper. By the Karhunen-Loeve (K-L expansion and the orthogonal polynomial approximation, the equivalent deterministic van der Pol system can be deduced. Based on the bifurcation theory of nonlinear deterministic system, the critical value of bifurcation parameter is obtained and the influence of random strength δ and noise intensity σ on stochastic Hopf bifurcation in compound stochastic system is discussed. At last we found that increased δ can relocate the critical value of bifurcation parameter forward while increased σ makes it backward and the influence of δ is more sensitive than σ. The results are verified by numerical simulations.

Clinical application of self-expandable metallic stents in the treatment of malignant tracheal stenosis under general anesthesia

International Nuclear Information System (INIS)

Wang Weitao; Shi Haibin; Yang Zhengqiang; Liu Sheng; Zhou Chungao; Zhao Linbo; Xia Jinguo; Li Linsun

2009-01-01

Objective: To evaluate the safety and efficacy of self-expandable metallic stent placement for the treatment of malignant tracheal stenosis under general anesthesia and fluoroscopic guidance. Methods: Under general anesthesia the placement of self-expandable metallic stent was performed in 10 patients with malignant tracheal stenosis, the procedure was completed under fluoroscopic guidance in all patients. Results: Successful tracheal stenting was achieved in all 10 patients. In one patient, a Y-shaped stent was used as the tracheal carina was involved in the airway stenosis. The symptoms of dyspnea and asthma were markedly improved immediately after the implantation of stent in all patients. Conclusion: Tracheal implantation of self-expandable metallic stent under general anesthesia and fluoroscopic guidance is a safe and effective treatment for malignant tracheal stenosis, it can promptly relieve various symptoms caused by malignant tracheal stenosis and obviously improve patient's living quality, therefore,t his technique is of great value in clinical practice. (authors)

New treatment of iliac artery disease: focus on the Absolute Pro® Vascular Self-Expanding Stent System

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Gates L

2013-09-01

Full Text Available Lindsay Gates, Jeffrey Indes Vascular and Endovascular Surgery, Yale University School of Medicine, New Haven, CT, USA Abstract: Management of iliac artery disease has evolved over the years, from a surgical-only approach to a primarily endovascular-only approach as the first line treatment option. This has been continuously improved upon with the advent of new devices and applied technologies. Most recently in particular, the literature has shown good, reliable outcomes with the use of self-expandable stents in iliac artery atherosclerotic lesions. Nevertheless, no device is without its limitations, and the Absolute Pro® Vascular Self-Expanding Stent System was designed with the intent of overcoming some of the shortcomings of other available stents while maintaining acceptable postprocedural outcomes. Based on preliminary industry-acquired data, it has achieved these goals and appears to be an emergent competitor for the treatment of both focal and complex iliac artery lesions. Keywords: Absolute-Pro®, iliac stent, self-expanding stents, atherosclerotic disease

Stochastic bifurcation in a model of love with colored noise

Science.gov (United States)

Yue, Xiaokui; Dai, Honghua; Yuan, Jianping

2015-07-01

In this paper, we wish to examine the stochastic bifurcation induced by multiplicative Gaussian colored noise in a dynamical model of love where the random factor is used to describe the complexity and unpredictability of psychological systems. First, the dynamics in deterministic love-triangle model are considered briefly including equilibrium points and their stability, chaotic behaviors and chaotic attractors. Then, the influences of Gaussian colored noise with different parameters are explored such as the phase plots, top Lyapunov exponents, stationary probability density function (PDF) and stochastic bifurcation. The stochastic P-bifurcation through a qualitative change of the stationary PDF will be observed and bifurcation diagram on parameter plane of correlation time and noise intensity is presented to find the bifurcation behaviors in detail. Finally, the top Lyapunov exponent is computed to determine the D-bifurcation when the noise intensity achieves to a critical value. By comparison, we find there is no connection between two kinds of stochastic bifurcation.

Valve-sparing aortic root replacement and aortic valve repair in a patient with acromegaly and aortic root dilatation

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Karel Van Praet

2015-07-01

Full Text Available Aortic regurgitation and dilatation of the aortic root and ascending aorta are severe complications of acromegaly. The current trend for management of an aortic root aneurysm is valve-sparing root replacement as well as restoring the diameter of the aortic sinotubular junction (STJ and annulus. Our case report supports the recommendation that in patients with acromegaly, severe aortic root involvement may indicate the need for surgery.

Travelling waves and their bifurcations in the Lorenz-96 model

Science.gov (United States)

van Kekem, Dirk L.; Sterk, Alef E.

2018-03-01

In this paper we study the dynamics of the monoscale Lorenz-96 model using both analytical and numerical means. The bifurcations for positive forcing parameter F are investigated. The main analytical result is the existence of Hopf or Hopf-Hopf bifurcations in any dimension n ≥ 4. Exploiting the circulant structure of the Jacobian matrix enables us to reduce the first Lyapunov coefficient to an explicit formula from which it can be determined when the Hopf bifurcation is sub- or supercritical. The first Hopf bifurcation for F > 0 is always supercritical and the periodic orbit born at this bifurcation has the physical interpretation of a travelling wave. Furthermore, by unfolding the codimension two Hopf-Hopf bifurcation it is shown to act as an organising centre, explaining dynamics such as quasi-periodic attractors and multistability, which are observed in the original Lorenz-96 model. Finally, the region of parameter values beyond the first Hopf bifurcation value is investigated numerically and routes to chaos are described using bifurcation diagrams and Lyapunov exponents. The observed routes to chaos are various but without clear pattern as n → ∞.

Treatment of Pelvic Venous Spur (May-Thurner Syndrome) with Self-Expanding Metallic Endoprostheses

International Nuclear Information System (INIS)

Binkert, Christoph A.; Schoch, Eric; Stuckmann, Gerd; Largiader, Jon; Wigger, Pius; Schoepke, Wolfdietrich; Zollikofer, Christoph L.

1998-01-01

Purpose: The application of self-expanding metallic endoprostheses (stents) to treat symptomatic pelvic venous spurs as an alternative to surgery. Methods: Wallstents with a diameter from 14 to 16 mm and one Cragg stent were placed in the left common iliac vein of eight patients (seven women, one man; mean age 42 years) with a symptomatic pelvic venous spur (left deep venous thrombosis or post-thrombotic leg swelling). Four patients had surgical thrombectomy prior to stent placement. Results: Technical success with immediate reduction of left leg circumference was achieved in all eight patients. A primary patency rate of 100% was observed during an average follow-up of 3 years (range 10-121 months). There were no procedural or stent-related complications. Conclusion: The percutaneous transfemoral placement of self-expanding metallic stents is an effective minimally invasive alternative to surgery in the treatment of symptomatic pelvic venous spur

Comments on the Bifurcation Structure of 1D Maps

DEFF Research Database (Denmark)

Belykh, V.N.; Mosekilde, Erik

1997-01-01

-within-a-box structure of the total bifurcation set. This presents a picture in which the homoclinic orbit bifurcations act as a skeleton for the bifurcational set. At the same time, experimental results on continued subharmonic generation for piezoelectrically amplified sound waves, predating the Feigenbaum theory......, are called into attention....

Predicting bifurcation angle effect on blood flow in the microvasculature.

Science.gov (United States)

Yang, Jiho; Pak, Y Eugene; Lee, Tae-Rin

2016-11-01

Since blood viscosity is a basic parameter for understanding hemodynamics in human physiology, great amount of research has been done in order to accurately predict this highly non-Newtonian flow property. However, previous works lacked in consideration of hemodynamic changes induced by heterogeneous vessel networks. In this paper, the effect of bifurcation on hemodynamics in a microvasculature is quantitatively predicted. The flow resistance in a single bifurcation microvessel was calculated by combining a new simple mathematical model with 3-dimensional flow simulation for varying bifurcation angles under physiological flow conditions. Interestingly, the results indicate that flow resistance induced by vessel bifurcation holds a constant value of approximately 0.44 over the whole single bifurcation model below diameter of 60μm regardless of geometric parameters including bifurcation angle. Flow solutions computed from this new model showed substantial decrement in flow velocity relative to other mathematical models, which do not include vessel bifurcation effects, while pressure remained the same. Furthermore, when applying the bifurcation angle effect to the entire microvascular network, the simulation results gave better agreements with recent in vivo experimental measurements. This finding suggests a new paradigm in microvascular blood flow properties, that vessel bifurcation itself, regardless of its angle, holds considerable influence on blood viscosity, and this phenomenon will help to develop new predictive tools in microvascular research. Copyright © 2016 Elsevier Inc. All rights reserved.

Treatment of intracranial atherosclerotic stenoses with balloon dilatation and self-expanding stent deployment (WingSpan)

Energy Technology Data Exchange (ETDEWEB)

Henkes, H. [Robert Janker Klinik, Bonn (Germany); Alfried Krupp Krankenhaus, Klinik fuer Radiologie und Neuroradiologie, Essen (Germany); Miloslavski, E.; Lowens, S.; Reinartz, J. [Robert Janker Klinik, Bonn (Germany); Liebig, T.; Kuehne, D. [Alfried Krupp Krankenhaus, Klinik fuer Radiologie und Neuroradiologie, Essen (Germany)

2005-03-01

The endovascular treatment of atherosclerotic intracranial arterial stenoses has previously been based on balloon dilatation or the deployment of a balloon expandable stent. Both methods have advantages (balloon: flexibility; balloon expandable stent: high radial force) and drawbacks (balloon: risk of elastic recoil and dissection; balloon expandable stent: limited flexibility, risk of injury to the vessel due to excessive straightening, overexpansion at ends of stent). A new combination of balloon dilatation, followed by the deployment of a self-expanding microstent has been applied in 15 patients with atherosclerotic arterial stenoses, symptomatic despite medical treatment. An anatomically and clinically adequate result was achieved in all patients. The initial degree of stenosis was 72% (mean). Balloon dilatation resulted in an average residual stenosis of 54% (mean), reduced further to a mean of 38% after stent deployment. Arterial dissection, occlusion of the target artery or symptomatic distal emboli was not encountered. In one patient, a side branch occlusion occurred after dilatation of a M1 stenosis, with complete neurological recovery. All patients were either stable or improved 4 weeks after the treatment. Recurrent TIA did not occur in any patient. Balloon dilatation and subsequent deployment of a self-expandable stent for the treatment of symptomatic intracranial arterial stenoses combines the advantages of both techniques and allows a rapid, clinically effective and technically safe treatment of these frequently challenging lesions. (orig.)

Treatment of intracranial atherosclerotic stenoses with balloon dilatation and self-expanding stent deployment (WingSpan)

International Nuclear Information System (INIS)

Henkes, H.; Miloslavski, E.; Lowens, S.; Reinartz, J.; Liebig, T.; Kuehne, D.

2005-01-01

The endovascular treatment of atherosclerotic intracranial arterial stenoses has previously been based on balloon dilatation or the deployment of a balloon expandable stent. Both methods have advantages (balloon: flexibility; balloon expandable stent: high radial force) and drawbacks (balloon: risk of elastic recoil and dissection; balloon expandable stent: limited flexibility, risk of injury to the vessel due to excessive straightening, overexpansion at ends of stent). A new combination of balloon dilatation, followed by the deployment of a self-expanding microstent has been applied in 15 patients with atherosclerotic arterial stenoses, symptomatic despite medical treatment. An anatomically and clinically adequate result was achieved in all patients. The initial degree of stenosis was 72% (mean). Balloon dilatation resulted in an average residual stenosis of 54% (mean), reduced further to a mean of 38% after stent deployment. Arterial dissection, occlusion of the target artery or symptomatic distal emboli was not encountered. In one patient, a side branch occlusion occurred after dilatation of a M1 stenosis, with complete neurological recovery. All patients were either stable or improved 4 weeks after the treatment. Recurrent TIA did not occur in any patient. Balloon dilatation and subsequent deployment of a self-expandable stent for the treatment of symptomatic intracranial arterial stenoses combines the advantages of both techniques and allows a rapid, clinically effective and technically safe treatment of these frequently challenging lesions. (orig.)

Bursting oscillations, bifurcation and synchronization in neuronal systems

Energy Technology Data Exchange (ETDEWEB)

Wang Haixia [School of Science, Nanjing University of Science and Technology, Nanjing 210094 (China); Wang Qingyun, E-mail: drwangqy@gmail.com [Department of Dynamics and Control, Beihang University, Beijing 100191 (China); Lu Qishao [Department of Dynamics and Control, Beihang University, Beijing 100191 (China)

2011-08-15

Highlights: > We investigate bursting oscillations and related bifurcation in the modified Morris-Lecar neuron. > Two types of fast-slow bursters are analyzed in detail. > We show the properties of some crucial bifurcation points. > Synchronization transition and the neural excitability are explored in the coupled bursters. - Abstract: This paper investigates bursting oscillations and related bifurcation in the modified Morris-Lecar neuron. It is shown that for some appropriate parameters, the modified Morris-Lecar neuron can exhibit two types of fast-slow bursters, that is 'circle/fold cycle' bursting and 'subHopf/homoclinic' bursting with class 1 and class 2 neural excitability, which have different neuro-computational properties. By means of the analysis of fast-slow dynamics and phase plane, we explore bifurcation mechanisms associated with the two types of bursters. Furthermore, the properties of some crucial bifurcation points, which can determine the type of the burster, are studied by the stability and bifurcation theory. In addition, we investigate the influence of the coupling strength on synchronization transition and the neural excitability in two electrically coupled bursters with the same bursting type. More interestingly, the multi-time-scale synchronization transition phenomenon is found as the coupling strength varies.

Self-expanding stent-assisted middle cerebral artery recanalization: technical note

International Nuclear Information System (INIS)

Sauvageau, Eric; Levy, Elad I.

2006-01-01

Investigation into pharmacological and mechanical means of improving recanalization rates by intraarterial therapy has led to technological development. Angiographic recanalization has been associated with improvement in clinical outcome. A clot retriever has recently joined an imperfect armamentarium for intraarterial stroke therapy. In this report, we describe successful recanalization of an acute thrombotic occlusion of the inferior division of the middle cerebral artery (MCA) achieved with a self-expanding stent. An 82-year-old woman with a history of coronary atherosclerosis and previous cerebellar hemorrhage presented with a National Institutes of Health Stroke Scale (NIHSS) score of 11. Perfusion computed tomography imaging showed a left MCA territory deficit. Diffusion-weighted magnetic resonance (MR) imaging revealed a small punctiform insular hyperintensity. Angiography documented occlusion of the inferior division of the left MCA (Thrombolysis in Myocardial Infarction or Thrombolysis in Cerebral Infarction, TIMI/TICI, grade 0). Intraarterial delivery of eptifibatide to the occlusion site failed to recanalize the vessel. Deployment of a self-expanding stent in the occluded segment resulted in complete revascularization of the distal vascular bed. Angiography performed on the next day confirmed patency of the stented vessel segment (TIMI/TICI 3). The patient was discharged 3 days after the procedure (NIHSS 3). MR angiography obtained 3 months after the procedure documented left MCA patency. This technique may have a role worthy of further investigation in acute stroke therapy. (orig.)

Dynamic bifurcations on financial markets

International Nuclear Information System (INIS)

Kozłowska, M.; Denys, M.; Wiliński, M.; Link, G.; Gubiec, T.; Werner, T.R.; Kutner, R.; Struzik, Z.R.

2016-01-01

We provide evidence that catastrophic bifurcation breakdowns or transitions, preceded by early warning signs such as flickering phenomena, are present on notoriously unpredictable financial markets. For this we construct robust indicators of catastrophic dynamical slowing down and apply these to identify hallmarks of dynamical catastrophic bifurcation transitions. This is done using daily closing index records for the representative examples of financial markets of small and mid to large capitalisations experiencing a speculative bubble induced by the worldwide financial crisis of 2007-08.

Hopf bifurcation for tumor-immune competition systems with delay

Directory of Open Access Journals (Sweden)

Ping Bi

2014-01-01

Full Text Available In this article, a immune response system with delay is considered, which consists of two-dimensional nonlinear differential equations. The main purpose of this paper is to explore the Hopf bifurcation of a immune response system with delay. The general formula of the direction, the estimation formula of period and stability of bifurcated periodic solution are also given. Especially, the conditions of the global existence of periodic solutions bifurcating from Hopf bifurcations are given. Numerical simulations are carried out to illustrate the the theoretical analysis and the obtained results.

Application of a novel retrievable self-expanding stent in intracranial aneurysm treatment

International Nuclear Information System (INIS)

Yang Zhigang; Liu Jianmin; Xu Yi; Huang Qinghai; Hong Bo; Zhao Wenyuan; Zhao Rui

2008-01-01

Objective: To assess the value of a novel retrievable self-expanding stent system (LEO) in intracranial aneurysm treatment. Methods: 43 patients with 44 intracranial aneurysms treated with LEO stent were retrospectively analized, including 16 aneurysms with single-stent deployment, 25 with stent-assisted technique, 2 with double-stent deployment and one with double-stent assisted coils. Follow up was carried out through imaging and clinical course. Results: The stent was easy for repositioning and all the stents were delivered successfully, except 1 stent with unsatisfactory position, 1 with acute in-stent thrombosis. During follow up, 1 case showed chronic in-stent thrombus and one with intimal hyperplasia. 22 aneurysms got compact coiled during procedure. Among 29 follow up cases, 72.4% aneurysms were cured or improved, 13.8% were stable and three dissection aneurysms enlarged within short period and two patients died. Conclusion: The new retrievable self-expanding stent (LEO), with the advantages of controlled delivery, easy deployment and choice for various types is a valuable system for vascular reconstruction of intracranial aneurysm with thrombosis. (authors)

Aortic valve bypass

DEFF Research Database (Denmark)

Lund, Jens T; Jensen, Maiken Brit; Arendrup, Henrik

2013-01-01

In aortic valve bypass (AVB) a valve-containing conduit is connecting the apex of the left ventricle to the descending aorta. Candidates are patients with symptomatic aortic valve stenosis rejected for conventional aortic valve replacement (AVR) or transcatheter aortic valve implantation (TAVI). ...

Pierce instability and bifurcating equilibria

International Nuclear Information System (INIS)

Godfrey, B.B.

1981-01-01

The report investigates the connection between equilibrium bifurcations and occurrence of the Pierce instability. Electrons flowing from one ground plane to a second through an ion background possess a countable infinity of static equilibria, of which only one is uniform and force-free. Degeneracy of the uniform and simplest non-uniform equilibria at a certain ground plan separation marks the onset of the Pierce instability, based on a newly derived dispersion relation appropriate to all the equilibria. For large ground plane separations the uniform equilibrium is unstable and the non-uniform equilibrium is stable, the reverse of their stability properties at small separations. Onset of the Pierce instability at the first bifurcation of equilibria persists in more complicated geometries, providing a general criterion for marginal stability. It seems probable that bifurcation analysis can be a useful tool in the overall study of stable beam generation in diodes and transport in finite cavities

Correction of aortic insufficiency with an external adjustable prosthetic aortic ring.

Science.gov (United States)

Gogbashian, Andrew; Ghanta, Ravi K; Umakanthan, Ramanan; Rangaraj, Aravind T; Laurence, Rita G; Fox, John A; Cohn, Lawrence H; Chen, Frederick Y

2007-09-01

Less invasive, valve-sparing options are needed for patients with aortic insufficiency (AI). We sought to evaluate the feasibility of reducing AI with an external adjustable aortic ring in an ovine model. To create AI, five sheep underwent patch plasty enlargement of the aortic annulus and root by placement of a 10 x 15 mm pericardial patch between the right and noncoronary cusps. An adjustable external ring composed of a nylon band was fabricated and placed around the aortic root. Aortic flow, aortic pressure, and left ventricular pressures were measured with the ring loose (off) and tightened (on). Mean regurgitant orifice area decreased by 86%, from 0.07 +/- 0.03 cm2 (ring loose, off) to 0.01 +/- 0.00 cm2 (ring tightened, on) [p < 0.01]. The regurgitant fraction decreased from 18 +/- 4% to 2 +/- 1% [p < 0.01]. The ring did not significantly affect stroke volume and aortic pressure. An ovine model of aortic root dilatation resulting in acute AI has been developed. In this model, application of an external, adjustable constricting aortic ring eliminated AI. An aortic ring may be a useful adjunct in reducing AI secondary to annular dilatation.

3D bioprinting of biomimetic aortic vascular constructs with self-supporting cells.

Science.gov (United States)

Kucukgul, Can; Ozler, S Burce; Inci, Ilyas; Karakas, Ezgi; Irmak, Ster; Gozuacik, Devrim; Taralp, Alpay; Koc, Bahattin

2015-04-01

Cardiovascular diseases are the leading cause of deaths throughout the world. Vascular diseases are mostly treated with autografts and blood vessel transplantations. However, traditional grafting methods have several problems including lack of suitable harvest sites, additional surgical costs for harvesting procedure, pain, infection, lack of donors, and even no substitutes at all. Recently, tissue engineering and regenerative medicine approaches are used to regenerate damaged or diseased tissues. Most of the tissue engineering investigations have been based on the cell seeding into scaffolds by providing a suitable environment for cell attachment, proliferation, and differentiation. Because of the challenges such as difficulties in seeding cells spatially, rejection, and inflammation of biomaterials used, the recent tissue engineering studies focus on scaffold-free techniques. In this paper, the development of novel computer aided algorithms and methods are developed for 3D bioprinting of scaffold-free biomimetic macrovascular structures. Computer model mimicking a real human aorta is generated using imaging techniques and the proposed computational algorithms. An optimized three-dimensional bioprinting path planning are developed with the proposed self-supported model. Mouse embryonic fibroblast (MEF) cell aggregates and support structures (hydrogels) are 3D bioprinted layer-by-layer according to the proposed self-supported method to form an aortic tissue construct. © 2014 Wiley Periodicals, Inc.

Chemotherapy versus self-expanding metal stent as primary treatment of severe dysphagia from unresectable oesophageal or gastro-oesophageal junction cancer.

Science.gov (United States)

Touchefeu, Yann; Archambeaud, Isabelle; Landi, Bruno; Lièvre, Astrid; Lepère, Céline; Rougier, Philippe; Mitry, Emmanuel

2014-03-01

To compare chemotherapy first (group 1) versus self-expanding metal stent first (group 2) for the management of malignant dysphagia in unresectable oesophageal or gastro-oesophageal junction cancer. Patients from two university hospitals with severe malignant dysphagia (dysphagia score ≥ 2) uneligible for surgery or radiochemotherapy were evaluated retrospectively. Forty-two patients were included in group 1, and 29 in group 2. After 4 weeks, dysphagia scores improved by at least 1 point in 67% of patients in group 1 versus 93% in group 2 (p=0.01); 48% of patients in group 1 were able to eat solid food versus 68% in group 2 (p=0.054). In group 1, a self-expanding metal stent was secondarily placed in 18 patients (42.9%), whereas in group 2 dysphagia required a second self-expanding metal stent placement in 33.3% of patients. Chemotherapy as the first treatment may be a valid option, avoiding self-expanding metal stent insertion in half of the patients. Copyright © 2013 Editrice Gastroenterologica Italiana S.r.l. Published by Elsevier Ltd. All rights reserved.

Aortic compliance in patients with aortic regurgitation. Evaluation with magnetic resonance imaging

International Nuclear Information System (INIS)

Murai, Sachiko; Hamada, Seiki; Ueguchi, Takashi

2005-01-01

The purpose of this study was to assess by means of cine magnetic resonance imaging (MRI) aortic compliance before and after aortic valve replacement (AVR with SJM (St. Jude Medical, St paul, MN) valve) in patients with aortic regurgitation (AR). Two groups (healthy controls and patients with severe isolated AR) of 10 subjects each were included in this study. Cine MRI was performed at three locations of the aorta, and aortic compliance was calculated by dividing the maximum change in the aortic area by pulse pressure. Cine MRI is useful to assess abnormalities of aortic compliance in patients with AR. Compared with the control group, aortic compliance in the AR group was significantly less in the ascending aorta (p<0.05), decreasing in order of aortic location. After AVR, aortic compliance improved for all locations. Cine MRI enables assessment of aortic biophysical properties such as a compliance for evaluating the progression of AR and the efficacy of treatment. (author)

Bifurcations of optimal vector fields: an overview

NARCIS (Netherlands)

Kiseleva, T.; Wagener, F.; Rodellar, J.; Reithmeier, E.

2009-01-01

We develop a bifurcation theory for the solution structure of infinite horizon optimal control problems with one state variable. It turns out that qualitative changes of this structure are connected to local and global bifurcations in the state-costate system. We apply the theory to investigate an

Acute Type II Aortic Dissection with Severe Aortic Regurgitation and Chronic Descending Aortic Dissection in Pregnant Patient with Marfan Syndrome.

Science.gov (United States)

Lee, Seok-Soo; Jung, Tae-Eun; Lee, Dong Hyup

2012-12-01

Aortic dilatation and dissection are severe complications during pregnancy that can be fatal to both the mother and the fetus. The risks of these complications are especially high in pregnant patients with Marfan syndrome; however, incidents of descending aortic dissection are very rare. This case report involves a successful Bentall procedure for and recovery from a rare aortic dissection in a pregnant Marfan patient who developed acute type II aortic dissection with severe aortic regurgitation and chronic descending aortic dissection immediately after Cesarean section. Regular follow-up will be needed to monitor the descending aortic dissection.

Bifurcations of transition states: Morse bifurcations

International Nuclear Information System (INIS)

MacKay, R S; Strub, D C

2014-01-01

A transition state for a Hamiltonian system is a closed, invariant, oriented, codimension-2 submanifold of an energy level that can be spanned by two compact codimension-1 surfaces of unidirectional flux whose union, called a dividing surface, locally separates the energy level into two components and has no local recrossings. For this to happen robustly to all smooth perturbations, the transition state must be normally hyperbolic. The dividing surface then has locally minimal geometric flux through it, giving an upper bound on the rate of transport in either direction. Transition states diffeomorphic to S 2m−3 are known to exist for energies just above any index-1 critical point of a Hamiltonian of m degrees of freedom, with dividing surfaces S 2m−2 . The question addressed here is what qualitative changes in the transition state, and consequently the dividing surface, may occur as the energy or other parameters are varied? We find that there is a class of systems for which the transition state becomes singular and then regains normal hyperbolicity with a change in diffeomorphism class. These are Morse bifurcations. Various examples are considered. Firstly, some simple examples in which transition states connect or disconnect, and the dividing surface may become a torus or other. Then, we show how sequences of Morse bifurcations producing various interesting forms of transition state and dividing surface are present in reacting systems, by considering a hypothetical class of bimolecular reactions in gas phase. (paper)

Regularization of the Boundary-Saddle-Node Bifurcation

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Xia Liu

2018-01-01

Full Text Available In this paper we treat a particular class of planar Filippov systems which consist of two smooth systems that are separated by a discontinuity boundary. In such systems one vector field undergoes a saddle-node bifurcation while the other vector field is transversal to the boundary. The boundary-saddle-node (BSN bifurcation occurs at a critical value when the saddle-node point is located on the discontinuity boundary. We derive a local topological normal form for the BSN bifurcation and study its local dynamics by applying the classical Filippov’s convex method and a novel regularization approach. In fact, by the regularization approach a given Filippov system is approximated by a piecewise-smooth continuous system. Moreover, the regularization process produces a singular perturbation problem where the original discontinuous set becomes a center manifold. Thus, the regularization enables us to make use of the established theories for continuous systems and slow-fast systems to study the local behavior around the BSN bifurcation.

Codimension-Two Bifurcation Analysis in DC Microgrids Under Droop Control

Science.gov (United States)

Lenz, Eduardo; Pagano, Daniel J.; Tahim, André P. N.

This paper addresses local and global bifurcations that may appear in electrical power systems, such as DC microgrids, which recently has attracted interest from the electrical engineering society. Most sources in these networks are voltage-type and operate in parallel. In such configuration, the basic technique for stabilizing the bus voltage is the so-called droop control. The main contribution of this work is a codimension-two bifurcation analysis of a small DC microgrid considering the droop control gain and the power processed by the load as bifurcation parameters. The codimension-two bifurcation set leads to practical rules for achieving a robust droop control design. Moreover, the bifurcation analysis also offers a better understanding of the dynamics involved in the problem and how to avoid possible instabilities. Simulation results are presented in order to illustrate the bifurcation analysis.

Flame Speed and Self-Similar Propagation of Expanding Turbulent Premixed Flames

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Chaudhuri, Swetaprovo; Wu, Fujia; Zhu, Delin; Law, Chung K.

2012-01-01

In this Letter we present turbulent flame speeds and their scaling from experimental measurements on constant-pressure, unity Lewis number expanding turbulent flames, propagating in nearly homogeneous isotropic turbulence in a dual-chamber, fan-stirred vessel. It is found that the normalized turbulent flame speed as a function of the average radius scales as a turbulent Reynolds number to the one-half power, where the average radius is the length scale and the thermal diffusivity is the transport property, thus showing self-similar propagation. Utilizing this dependence it is found that the turbulent flame speeds from the present expanding flames and those from the Bunsen geometry in the literature can be unified by a turbulent Reynolds number based on flame length scales using recent theoretical results obtained by spectral closure of the transformed G equation.

Aortic root replacement after previous surgical intervention on the aortic valve, aortic root, or ascending aorta.

Science.gov (United States)

Kirsch, E W Matthias; Radu, N Costin; Mekontso-Dessap, Armand; Hillion, Marie-Line; Loisance, Daniel

2006-03-01

Aortic root replacement after a previous operation on the aortic valve, aortic root, or ascending aorta remains a major challenge. Records of 56 consecutive patients (44 men; mean age, 56.4 +/- 13.6 years) undergoing reoperative aortic root replacement between June 1994 and June 2005 were reviewed retrospectively. Reoperation was performed 9.4 +/- 6.7 years after the last cardiac operation. Indications for reoperation were true aneurysm (n = 14 [25%]), false aneurysm (n = 10 [18%]), dissection or redissection (n = 9 [16%]), structural or nonstructural valve dysfunction (n = 10 [18%]), prosthetic valve-graft infection (n = 12 [21%]), and miscellaneous (n = 1 [2%]). Procedures performed were aortic root replacement (n = 47 [84%]), aortic root replacement plus mitral valve procedure (n = 5 [9%]), and aortic root replacement plus arch replacement (n = 4 [7%]). In 14 (25%) patients coronary artery bypass grafting had to be performed unexpectedly during the same procedure or immediately after the procedure to re-establish coronary perfusion. Hospital mortality reached 17.9% (n = 10). Multivariate logistic regression analysis revealed the need for unplanned perioperative coronary artery bypass grafting as the sole independent risk factor for hospital death (P = .005). Actuarial survival was 83.8% +/- 4.9% at 1 month, 73.0% +/- 6.3% at 1 year, and 65.7% +/- 9.0% at 5 years after the operation. One patient had recurrence of endocarditis 6.7 months after the operation and required repeated homograft aortic root replacement. Reoperative aortic root replacement remains associated with a high postoperative mortality. The need to perform unplanned coronary artery bypass grafting during reoperative aortic root replacement is a major risk factor for hospital death. The optimal technique for coronary reconstruction in this setting remains to be debated.

Bifurcation diagram of a cubic three-parameter autonomous system

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Lenka Barakova

2005-07-01

Full Text Available In this paper, we study the cubic three-parameter autonomous planar system $$displaylines{ dot x_1 = k_1 + k_2x_1 - x_1^3 - x_2,cr dot x_2 = k_3 x_1 - x_2, }$$ where $k_2, k_3$ are greater than 0. Our goal is to obtain a bifurcation diagram; i.e., to divide the parameter space into regions within which the system has topologically equivalent phase portraits and to describe how these portraits are transformed at the bifurcation boundaries. Results may be applied to the macroeconomical model IS-LM with Kaldor's assumptions. In this model existence of a stable limit cycles has already been studied (Andronov-Hopf bifurcation. We present the whole bifurcation diagram and among others, we prove existence of more difficult bifurcations and existence of unstable cycles.

Bifurcation of transition paths induced by coupled bistable systems.

Science.gov (United States)

Tian, Chengzhe; Mitarai, Namiko

2016-06-07

We discuss the transition paths in a coupled bistable system consisting of interacting multiple identical bistable motifs. We propose a simple model of coupled bistable gene circuits as an example and show that its transition paths are bifurcating. We then derive a criterion to predict the bifurcation of transition paths in a generalized coupled bistable system. We confirm the validity of the theory for the example system by numerical simulation. We also demonstrate in the example system that, if the steady states of individual gene circuits are not changed by the coupling, the bifurcation pattern is not dependent on the number of gene circuits. We further show that the transition rate exponentially decreases with the number of gene circuits when the transition path does not bifurcate, while a bifurcation facilitates the transition by lowering the quasi-potential energy barrier.

Improvement of quality of life and survival using self-expandable metal stent placement for severe malignant stenosis of the gastric body: a case report

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Kumagai Hozumi

2012-09-01

Full Text Available Abstract Introduction Advanced gastric carcinoma often decreases quality of life because of upper gastrointestinal tract stenosis. Self-expandable metal stents have been thought to be an effective, minimally invasive treatment for stenosis. However, the effectiveness of self-expandable metal stent placement for carcinomatous stenosis of the gastric body and antrum has not been clarified, and there have been few reports of such cases. Case presentation A 74-year-old Japanese woman developed stenosis of the gastric body and antrum caused by advanced gastric cancer during first-line chemotherapy. She developed weight loss and poor nutrition due to inadequate intake. Self-expandable metal stent placement for stenosis of the gastric body and antrum ameliorated her symptoms rapidly and improved her general condition and quality of life. Eight days after self-expandable metal stent placement, second-line chemotherapy could be administered safely. Oral intake and nutritional status were maintained for 117 days after self-expandable metal stent placement, and she died of gastric cancer 176 days after self-expandable metal stent placement and initiation of second-line chemotherapy. Conclusions Self-expandable metal stent placement for carcinomatous stenosis in the gastric body and antrum could be an effective therapeutic strategy for patients with inadequate oral uptake. It may provide rapid improvement of the patient’s general condition and oral intake with minimal complications, comparatively long-term symptom relief, and a survival benefit by allowing second-line chemotherapy.

Self-expandable metal stents for malignant colonic obstruction: data from a retrospective regional SIED-AIGO study.

Science.gov (United States)

Di Mitri, Roberto; Mocciaro, Filippo; Traina, Mario; Montalbano, Luigi Maria; Familiari, Luigi; D'Amore, Fabio; Raimondo, Dario; Virgilio, Clara; Tarantino, Ilaria; Barresi, Luca; Giunta, Marco; Borina, Eleonora; Borruto, Antonino; Marino, Antonino

2014-03-01

Self-expandable metal stents are a non-surgical option for the treatment of symptomatic malignant colorectal obstruction as palliative treatment or as a bridge to surgery. To report data from a regional study on self-expandable metal stent (SEMS) placement for malignant colorectal obstruction. Two hundred and four patients (male 54.9%, mean age of 69.5 ± 14.2) were retrospectively evaluated and data on technical and clinical success, and complications, were analyzed. Technical and clinical success rates were 99% and 94.6% respectively, with 36.7% treated on an emergency basis and 63.3% electively. Palliative treatment was administered to 70.1%, and as a bridge to surgery for 29.9%. Complications were 17 neoplastic ingrowths, 10 stent migrations, and 4 perforations. Palliative treatment was associated with a higher risk of stent ingrowth (p=0.003), and chemotherapy with a lower risk of stent ingrowth (p=0.009). This regional study, although it has certain limitations, confirms the positive role of self-expandable metal stents in the treatment of symptomatic malignant colorectal obstruction, and that chemotherapy decreases the risk of ingrowth. Copyright © 2013 Editrice Gastroenterologica Italiana S.r.l. Published by Elsevier Ltd. All rights reserved.

Analysis of zonal flow bifurcations in 3D drift wave turbulence simulations

International Nuclear Information System (INIS)

Kammel, Andreas

2012-01-01

The main issue of experimental magnetic fusion devices lies with their inherently high turbulent transport, preventing long-term plasma confinement. A deeper understanding of the underlying transport processes is therefore desirable, especially in the high-gradient tokamak edge which marks the location of the drift wave regime as well as the outer boundary of the still badly understood high confinement mode. One of the most promising plasma features possibly connected to a complete bifurcation theory for the transition to this H-mode is found in large-scale phenomena capable of regulating radial transport through vortex shearing - i.e. zonal flows, linearly stable large-scale poloidal vector E x vector B-modes based on radial flux surface averages of the potential gradient generated through turbulent self-organization. Despite their relevance, few detailed turbulence studies of drift wave-based zonal flows have been undertaken, and none of them have explicitly targeted bifurcations - or, within a resistive sheared-slab environment, observed zonal flows at all. In this work, both analytical means and the two-fluid code NLET are used to analyze a reduced set of Hasegawa-Wakatani equations, describing a sheared collisional drift wave system without curvature. The characteristics of the drift waves themselves, as well as those of the drift wave-based zonal flows and their retroaction on the drift wave turbulence are examined. The single dimensionless parameter ρ s proposed in previous analytical models is examined numerically and shown to divide the drift wave scale into two transport regimes, the behavioral characteristics of which agree perfectly with theoretical expectations. This transport transition correlates with a transition from pure drift wave turbulence at low ρ s into the high-ρ s zonal flow regime. The associated threshold has been more clearly identified by tracing it back to a tipping of the ratio between a newly proposed frequency gradient length at

Self-expandable metal stents for relieving malignant colorectal obstruction: short-term safety and efficacy within 30 days of stent procedure in 447 patients

DEFF Research Database (Denmark)

Meisner, Søren; González-Huix, Ferran; Vandervoort, Jo G

2011-01-01

The self-expandable metal stent (SEMS) can alleviate malignant colonic obstruction and avoid emergency decompressive surgery.......The self-expandable metal stent (SEMS) can alleviate malignant colonic obstruction and avoid emergency decompressive surgery....

Percutaneous coronary intervention for the left main stem and other bifurcation lesions: 12th consensus document from the European Bifurcation Club.

Science.gov (United States)

Lassen, Jens Flensted; Burzotta, Francesco; Banning, Adrian P; Lefèvre, Thierry; Darremont, Olivier; Hildick-Smith, David; Chieffo, Alaide; Pan, Manuel; Holm, Niels Ramsing; Louvard, Yves; Stankovic, Goran

2018-01-20

The European Bifurcation Club (EBC) was initiated in 2004 to support a continuous overview of the field of coronary artery bifurcation interventions and aims to facilitate a scientific discussion and an exchange of ideas on the management of bifurcation disease. The EBC hosts an annual, two-day compact meeting, dedicated to bifurcations, which brings together physicians, pathologists, engineers, biologists, physicists, mathematicians, epidemiologists and statisticians for detailed discussions. Every meeting is finalised with a consensus statement that reflects the unique opportunity of combining the opinion of interventional cardiologists with the opinion of a large variety of other scientists on bifurcation management. A series of consensus sessions dedicated to specific topics, to strengthen the consensus debates and focus the discussions, was introduced at this year's meeting. The sessions comprise an intensive overview of the present literature, a pro and con debate and a voting system, to guide the consensus-building process. The present document represents the summary of the up-to-date EBC consensus and recommendations from the 12th annual EBC meeting in 2016 in Rotterdam.

Nonlinear physical systems spectral analysis, stability and bifurcations

CERN Document Server

Kirillov, Oleg N

2013-01-01

Bringing together 18 chapters written by leading experts in dynamical systems, operator theory, partial differential equations, and solid and fluid mechanics, this book presents state-of-the-art approaches to a wide spectrum of new and challenging stability problems.Nonlinear Physical Systems: Spectral Analysis, Stability and Bifurcations focuses on problems of spectral analysis, stability and bifurcations arising in the nonlinear partial differential equations of modern physics. Bifurcations and stability of solitary waves, geometrical optics stability analysis in hydro- and magnetohydrodynam

Fractional noise destroys or induces a stochastic bifurcation

Energy Technology Data Exchange (ETDEWEB)

Yang, Qigui, E-mail: qgyang@scut.edu.cn [School of Sciences, South China University of Technology, Guangzhou 510640 (China); Zeng, Caibin, E-mail: zeng.cb@mail.scut.edu.cn [School of Sciences, South China University of Technology, Guangzhou 510640 (China); School of Automation Science and Engineering, South China University of Technology, Guangzhou 510640 (China); Wang, Cong, E-mail: wangcong@scut.edu.cn [School of Automation Science and Engineering, South China University of Technology, Guangzhou 510640 (China)

2013-12-15

Little seems to be known about the stochastic bifurcation phenomena of non-Markovian systems. Our intention in this paper is to understand such complex dynamics by a simple system, namely, the Black-Scholes model driven by a mixed fractional Brownian motion. The most interesting finding is that the multiplicative fractional noise not only destroys but also induces a stochastic bifurcation under some suitable conditions. So it opens a possible way to explore the theory of stochastic bifurcation in the non-Markovian framework.

Biodegradable shape-memory block co-polymers for fast self-expandable stents.

Science.gov (United States)

Xue, Liang; Dai, Shiyao; Li, Zhi

2010-11-01

Block co-polymers PCTBVs (M(n) of 36,300-65,300 g/mol, T(m) of 39-40 and 142 degrees C) containing hyperbranched three-arm poly(epsilon-caprolactone) (PCL) as switching segment and microbial polyester PHBV as crystallizable hard segment were designed as biodegradable shape-memory polymer (SMP) for fast self-expandable stent and synthesized in 96% yield by the reaction of three-arm PCL-triol (M(n) of 4200 g/mol, T(m) of 47 degrees C) with methylene diphenyl 4,4'-diisocyanate isocynate (MDI) to form the hyperbrached MDI-linked PCL (PTCM; M(n) of 25,400 g/mol and a T(m) of 38 degrees C), followed by further polymerization with PHBV-diol (M(n) of 2200 g/mol, T(m) of 137 and 148 degrees C). The polymers were characterized by (1)H NMR, GPC, DSC, tensile test, and cyclic thermomechanical tensile test. PCTBVs showed desired thermal properties, mechanical properties, and ductile nature. PCTBV containing 25 wt% PHBV (PCTBV-25) demonstrated excellent shape-memory property at 40 degrees C, with R(f) of 94%, R(r) of 98%, and shape recovery within 25s. PCTBV-25 was also shown as a safe material with good biocompatibility by cytotoxicity tests and cell growth experiments. The stent made from PCTBV-25 film showed nearly complete self-expansion at 37 degrees C within only 25 s, which is much better and faster than the best known self-expandable stents. Copyright (c) 2010 Elsevier Ltd. All rights reserved.

Global Hopf Bifurcation for a Predator-Prey System with Three Delays

Science.gov (United States)

Jiang, Zhichao; Wang, Lin

2017-06-01

In this paper, a delayed predator-prey model is considered. The existence and stability of the positive equilibrium are investigated by choosing the delay τ = τ1 + τ2 as a bifurcation parameter. We see that Hopf bifurcation can occur as τ crosses some critical values. The direction of the Hopf bifurcations and the stability of the bifurcation periodic solutions are also determined by using the center manifold and normal form theory. Furthermore, based on the global Hopf bifurcation theorem for general function differential equations, which was established by J. Wu using fixed point theorem and degree theory methods, the existence of global Hopf bifurcation is investigated. Finally, numerical simulations to support the analytical conclusions are carried out.

Codimension-two bifurcation analysis on firing activities in Chay neuron model

International Nuclear Information System (INIS)

Duan Lixia; Lu Qishao

2006-01-01

Using codimension-two bifurcation analysis in the Chay neuron model, the relationship between the electric activities and the parameters of neurons is revealed. The whole parameter space is divided into two parts, that is, the firing and silence regions of neurons. It is found that the transition sets between firing and silence regions are composed of the Hopf bifurcation curves of equilibrium states and the saddle-node bifurcation curves of limit cycles, with some codimension-two bifurcation points. The transitions from silence to firing in neurons are due to the Hopf bifurcation or the fold limit cycle bifurcation, but the codimension-two singularities lead to complexity in dynamical behaviour of neuronal firing

Codimension-two bifurcation analysis on firing activities in Chay neuron model

Energy Technology Data Exchange (ETDEWEB)

Duan Lixia [School of Science, Beijing University of Aeronautics and Astronautics, Beijing 100083 (China); Lu Qishao [School of Science, Beijing University of Aeronautics and Astronautics, Beijing 100083 (China)]. E-mail: qishaolu@hotmail.com

2006-12-15

Using codimension-two bifurcation analysis in the Chay neuron model, the relationship between the electric activities and the parameters of neurons is revealed. The whole parameter space is divided into two parts, that is, the firing and silence regions of neurons. It is found that the transition sets between firing and silence regions are composed of the Hopf bifurcation curves of equilibrium states and the saddle-node bifurcation curves of limit cycles, with some codimension-two bifurcation points. The transitions from silence to firing in neurons are due to the Hopf bifurcation or the fold limit cycle bifurcation, but the codimension-two singularities lead to complexity in dynamical behaviour of neuronal firing.

Delayed Presentation of a Giant Ascending Aortic Aneurysm following Aortic Valve Replacement

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Tugrul Göncü

2009-01-01

Full Text Available Giant ascending aortic aneurysm formation following aortic valve replacement is rare. A 28-year-old man who underwent aortic valve replacement with a prosthetic valve for aortic regurgitation secondary to congenital bicuspid aortic valve about 10 years ago was diagnosed with a giant ascending aortic aneurysm about 16 cm in diameter in follow-up. The aneurysm was resected leaving the functional old mechanical prosthesis in place and implanted a 34-mm Hemashield woven graft, associated with the left and right coronary artery button implantation. Histological findings of the aortic aneurysm wall showed cystic medial necrosis. The postoperative course was uneventful and postoperative examination demonstrated good surgical results.

Bifurcation magnetic resonance in films magnetized along hard magnetization axis

Energy Technology Data Exchange (ETDEWEB)

Vasilevskaya, Tatiana M., E-mail: t_vasilevs@mail.ru [Ulyanovsk State University, Leo Tolstoy 42, 432017 Ulyanovsk (Russian Federation); Sementsov, Dmitriy I.; Shutyi, Anatoliy M. [Ulyanovsk State University, Leo Tolstoy 42, 432017 Ulyanovsk (Russian Federation)

2012-09-15

We study low-frequency ferromagnetic resonance in a thin film magnetized along the hard magnetization axis performing an analysis of magnetization precession dynamics equations and numerical simulation. Two types of films are considered: polycrystalline uniaxial films and single-crystal films with cubic magnetic anisotropy. An additional (bifurcation) resonance initiated by the bistability, i.e. appearance of two closely spaced equilibrium magnetization states is registered. The modification of dynamic modes provoked by variation of the frequency, amplitude, and magnetic bias value of the ac field is studied. Both steady and chaotic magnetization precession modes are registered in the bifurcation resonance range. - Highlights: Black-Right-Pointing-Pointer An additional bifurcation resonance arises in a case of a thin film magnetized along HMA. Black-Right-Pointing-Pointer Bifurcation resonance occurs due to the presence of two closely spaced equilibrium magnetization states. Black-Right-Pointing-Pointer Both regular and chaotic precession modes are realized within bifurcation resonance range. Black-Right-Pointing-Pointer Appearance of dynamic bistability is typical for bifurcation resonance.

Bifurcation magnetic resonance in films magnetized along hard magnetization axis

International Nuclear Information System (INIS)

Vasilevskaya, Tatiana M.; Sementsov, Dmitriy I.; Shutyi, Anatoliy M.

2012-01-01

We study low-frequency ferromagnetic resonance in a thin film magnetized along the hard magnetization axis performing an analysis of magnetization precession dynamics equations and numerical simulation. Two types of films are considered: polycrystalline uniaxial films and single-crystal films with cubic magnetic anisotropy. An additional (bifurcation) resonance initiated by the bistability, i.e. appearance of two closely spaced equilibrium magnetization states is registered. The modification of dynamic modes provoked by variation of the frequency, amplitude, and magnetic bias value of the ac field is studied. Both steady and chaotic magnetization precession modes are registered in the bifurcation resonance range. - Highlights: ► An additional bifurcation resonance arises in a case of a thin film magnetized along HMA. ► Bifurcation resonance occurs due to the presence of two closely spaced equilibrium magnetization states. ► Both regular and chaotic precession modes are realized within bifurcation resonance range. ► Appearance of dynamic bistability is typical for bifurcation resonance.

Complication after self expandable metallic stent for esophageal cancer

International Nuclear Information System (INIS)

Nagahama, Takeshi; Maruyama, Michio; Kato, Kiyomi; Shinoura, Hiroshi; Hasegawa, Kumi; Takashima, Itaru; Ebuchi, Masakazu

2003-01-01

Major complications after placement of esophageal stent and airway stent were reviewed and evaluated. Four patients, including two patients with perforations and two patients with fistula formation, developed major complications after placement of a self expandable metallic stent. Two patients underwent additional radiation to improve stricture after stent placement. In one patient, stent placement was selected to improve esophageal stricture that occurred after radical radiation therapy. In one patient, migration of stent into the lesion caused a perforation. It can be concluded that additional radiation after stent placement increases the risk of complication. Stent migration also can lead to the risk of perforation. (author)

Self-expandable metallic stents for patients with recurrent esophageal carcinoma after failure of primary chemoradiotherapy

Energy Technology Data Exchange (ETDEWEB)

Muto, Manabu; Ohtsu, Atsushi; Boku, Narikazu; Yoshida, Shigeaki [National Cancer Center, Kashiwa, Chiba (Japan). Hospital East; Miyata, Yoshinori; Shioyama, Yasukazu

2001-06-01

Recent advances in chemoradiotherapy for esophageal carcinoma have resulted in improved survival rates. However, there are few options for recurrent dysphagia due to refractory carcinoma after failure of primary chemoradiotherapy. The aim of this study was to evaluate the safety and efficacy of self-expandable metallic stent placement for patients with recurrent esophageal carcinoma where definitive chemoradiotherapy has failed. Thirteen consecutive patients with recurrent squamous cell carcinoma of the esophagus, in whom self-expandable metallic stents were placed after failure of primary chemoradiotherapy, were studied retrospectively. All patients had esophageal obstruction or malignant fistula. The oral alimentation status of nine of 13 patients (69%) improved after successful placement of the stent. Following placement of the stent, fever (>38 deg C) and severe chest pain occurred in 85% (11/13) of the patients. In all patients examined, C-reactive protein was elevated within 1 week of the operation. Esophageal perforation occurred in three patients. Stent-related mediastinitis and pneumonia developed in six (46%) and three (23%) patients, respectively. Seven of the 13 patients (54%) died of stent-related pulmonary complications. Although the placement of a self-expandable metallic stent for patients with recurrent esophageal carcinoma after failure of chemoradiotherapy improved their oral alimentation status, we found that this treatment increases the risk of life-threatening pulmonary complications. (author)

Self-expandable polytetrafluoroethylene (PTFE)-covered nitinol stent for the palliative treatment of malignant biliary obstruction

Energy Technology Data Exchange (ETDEWEB)

Yoo, Oong; Jung, Gyoo Sik; Han, Byung Hoon; Shin, Dong Hoon [Gospel Hospital, College of Medicine, Kosin University, Busan (Korea, Republic of); Ko, Ji Ho [Masan Samsung Medical Center, Sungkyunkwan University School of Medicine, Masan (Korea, Republic of)

2008-06-15

We wanted to determine the technical and clinical efficacy of placing a self-expandable PTFE-covered nitinol stent for the management of inoperable malignant biliary obstruction. Thirty six patients with inoperable malignant biliary obstructions were treated by placement of self-expandable PTFE-covered nitinol stents (S and G Biotech Corporation, Seongnam, Korea). Clinical evaluation was done with assessment of the serum bilirubin and alkaline phosphatase levels, which were measured before and after stent placement within 1 week, at 1 month and at 3 months. The patient survival rate and stent patency rate were calculated with performing Kaplan-Meier survival analysis. Successful stent placement was achieved in all the patients without procedure-related complication. Pancreatitis as an early complication occurred in two cases. The serum bilirubin and alkaline phosphatase levels were significantly decreased after the procedure. During the follow-up, recurrent obstructive jaundice occurred in six cases; stent migration occurred in four cases and tumor overgrowth occurred in two cases. The survival rates were 97%, 80%, 67% and 59% at 1, 3, 6 and 9 months, respectively. The stent patency rates were 96%, 92%, 86% and 86% at 1, 3, 6 and 9 months, respectively. Self-expandable PTFE-covered nitinol stent placement seems to be technically feasible and effective for the palliative treatment of malignant biliary obstruction.

Self-expandable metallic stents for patients with recurrent esophageal carcinoma after failure of primary chemoradiotherapy

International Nuclear Information System (INIS)

Muto, Manabu; Ohtsu, Atsushi; Boku, Narikazu; Yoshida, Shigeaki; Miyata, Yoshinori; Shioyama, Yasukazu

2001-01-01

Recent advances in chemoradiotherapy for esophageal carcinoma have resulted in improved survival rates. However, there are few options for recurrent dysphagia due to refractory carcinoma after failure of primary chemoradiotherapy. The aim of this study was to evaluate the safety and efficacy of self-expandable metallic stent placement for patients with recurrent esophageal carcinoma where definitive chemoradiotherapy has failed. Thirteen consecutive patients with recurrent squamous cell carcinoma of the esophagus, in whom self-expandable metallic stents were placed after failure of primary chemoradiotherapy, were studied retrospectively. All patients had esophageal obstruction or malignant fistula. The oral alimentation status of nine of 13 patients (69%) improved after successful placement of the stent. Following placement of the stent, fever (>38 deg C) and severe chest pain occurred in 85% (11/13) of the patients. In all patients examined, C-reactive protein was elevated within 1 week of the operation. Esophageal perforation occurred in three patients. Stent-related mediastinitis and pneumonia developed in six (46%) and three (23%) patients, respectively. Seven of the 13 patients (54%) died of stent-related pulmonary complications. Although the placement of a self-expandable metallic stent for patients with recurrent esophageal carcinoma after failure of chemoradiotherapy improved their oral alimentation status, we found that this treatment increases the risk of life-threatening pulmonary complications. (author)

Self-expandable polytetrafluoroethylene (PTFE)-covered nitinol stent for the palliative treatment of malignant biliary obstruction

International Nuclear Information System (INIS)

Yoo, Oong; Jung, Gyoo Sik; Han, Byung Hoon; Shin, Dong Hoon; Ko, Ji Ho

2008-01-01

We wanted to determine the technical and clinical efficacy of placing a self-expandable PTFE-covered nitinol stent for the management of inoperable malignant biliary obstruction. Thirty six patients with inoperable malignant biliary obstructions were treated by placement of self-expandable PTFE-covered nitinol stents (S and G Biotech Corporation, Seongnam, Korea). Clinical evaluation was done with assessment of the serum bilirubin and alkaline phosphatase levels, which were measured before and after stent placement within 1 week, at 1 month and at 3 months. The patient survival rate and stent patency rate were calculated with performing Kaplan-Meier survival analysis. Successful stent placement was achieved in all the patients without procedure-related complication. Pancreatitis as an early complication occurred in two cases. The serum bilirubin and alkaline phosphatase levels were significantly decreased after the procedure. During the follow-up, recurrent obstructive jaundice occurred in six cases; stent migration occurred in four cases and tumor overgrowth occurred in two cases. The survival rates were 97%, 80%, 67% and 59% at 1, 3, 6 and 9 months, respectively. The stent patency rates were 96%, 92%, 86% and 86% at 1, 3, 6 and 9 months, respectively. Self-expandable PTFE-covered nitinol stent placement seems to be technically feasible and effective for the palliative treatment of malignant biliary obstruction

DISSECT: a new mnemonic-based approach to the categorization of aortic dissection.

Science.gov (United States)

Dake, M D; Thompson, M; van Sambeek, M; Vermassen, F; Morales, J P

2013-08-01

Classification systems for aortic dissection provide important guides to clinical decision-making, but the relevance of traditional categorization schemes is being questioned in an era when endovascular techniques are assuming a growing role in the management of this frequently complex and catastrophic entity. In recognition of the expanding range of interventional therapies now used as alternatives to conventional treatment approaches, the Working Group on Aortic Diseases of the DEFINE Project developed a categorization system that features the specific anatomic and clinical manifestations of the disease process that are most relevant to contemporary decision-making. The DISSECT classification system is a mnemonic-based approach to the evaluation of aortic dissection. It guides clinicians through an assessment of six critical characteristics that facilitate optimal communication of the most salient details that currently influence the selection of a therapeutic option, including those findings that are key when considering an endovascular procedure, but are not taken into account by the DeBakey or Stanford categorization schemes. The six features of aortic dissection include: duration of disease; intimal tear location; size of the dissected aorta; segmental extent of aortic involvement; clinical complications of the dissection, and thrombus within the aortic false lumen. In current clinical practice, endovascular therapy is increasingly considered as an alternative to medical management or open surgical repair in select cases of type B aortic dissection. Currently, endovascular aortic repair is not used for patients with type A aortic dissection, but catheter-based techniques directed at peripheral branch vessel ischemia that may complicate type A dissection are considered valuable adjunctive interventions, when indicated. The use of a new system for categorization of aortic dissection, DISSECT, addresses the shortcomings of well-known established schemes devised

Inverse bifurcation analysis: application to simple gene systems

Directory of Open Access Journals (Sweden)

Schuster Peter

2006-07-01

Full Text Available Abstract Background Bifurcation analysis has proven to be a powerful method for understanding the qualitative behavior of gene regulatory networks. In addition to the more traditional forward problem of determining the mapping from parameter space to the space of model behavior, the inverse problem of determining model parameters to result in certain desired properties of the bifurcation diagram provides an attractive methodology for addressing important biological problems. These include understanding how the robustness of qualitative behavior arises from system design as well as providing a way to engineer biological networks with qualitative properties. Results We demonstrate that certain inverse bifurcation problems of biological interest may be cast as optimization problems involving minimal distances of reference parameter sets to bifurcation manifolds. This formulation allows for an iterative solution procedure based on performing a sequence of eigen-system computations and one-parameter continuations of solutions, the latter being a standard capability in existing numerical bifurcation software. As applications of the proposed method, we show that the problem of maximizing regions of a given qualitative behavior as well as the reverse engineering of bistable gene switches can be modelled and efficiently solved.

Deformable 4DCT lung registration with vessel bifurcations

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Hilsmann, A.; Vik, T.; Kaus, M.; Franks, K.; Bissonette, J.P.; Purdie, T.; Beziak, A.; Aach, T.

2007-01-01

In radiotherapy planning of lung cancer, breathing motion causes uncertainty in the determination of the target volume. Image registration makes it possible to get information about the deformation of the lung and the tumor movement in the respiratory cycle from a few images. A dedicated, automatic, landmark-based technique was developed that finds corresponding vessel bifurcations. Hereby, we developed criteria to characterize pronounced bifurcations for which correspondence finding was more stable and accurate. The bifurcations were extracted from automatically segmented vessel trees in maximum inhale and maximum exhale CT thorax data sets. To find corresponding bifurcations in both data sets we used the shape context approach of Belongie et al. Finally, a volumetric lung deformation was obtained using thin-plate spline interpolation and affine registration. The method is evaluated on 10 4D-CT data sets of patients with lung cancer. (orig.)

Period-doubling bifurcation cascade observed in a ferromagnetic nanoparticle under the action of a spin-polarized current

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Horley, Paul P., E-mail: paul.horley@cimav.edu.mx [Centro de Investigación en Materiales Avanzados, S.C. (CIMAV), Chihuahua/Monterrey, 120 Avenida Miguel de Cervantes, 31109 Chihuahua (Mexico); Kushnir, Mykola Ya. [Yuri Fedkovych Chernivtsi National University, 2 Kotsyubynsky str., 58012 Chernivtsi (Ukraine); Morales-Meza, Mishel [Centro de Investigación en Materiales Avanzados, S.C. (CIMAV), Chihuahua/Monterrey, 120 Avenida Miguel de Cervantes, 31109 Chihuahua (Mexico); Sukhov, Alexander [Institut für Physik, Martin-Luther Universität Halle-Wittenberg, 06120 Halle (Saale) (Germany); Rusyn, Volodymyr [Yuri Fedkovych Chernivtsi National University, 2 Kotsyubynsky str., 58012 Chernivtsi (Ukraine)

2016-04-01

We report on complex magnetization dynamics in a forced spin valve oscillator subjected to a varying magnetic field and a constant spin-polarized current. The transition from periodic to chaotic magnetic motion was illustrated with bifurcation diagrams and Hausdorff dimension – the methods developed for dissipative self-organizing systems. It was shown that bifurcation cascades can be obtained either by tuning the injected spin-polarized current or by changing the magnitude of applied magnetic field. The order–chaos transition in magnetization dynamics can be also directly observed from the hysteresis curves. The resulting complex oscillations are useful for development of spin-valve devices operating in harmonic and chaotic modes.

The bicuspid aortic valve and its relation to aortic dilation

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Shi-Min Yuan

2010-01-01

Full Text Available BACKGROUND: A bicuspid aortic valve (BAV is a common congenital heart disease, which affects 1-2% of the population. However, the relationship between BAVs and aortic dilation has not been sufficiently elucidated. METHODS: A total of 241 BAV patients who were referred to this hospital for cardiac surgey over a 4.75-year period were included in this study. In addition to the clinical characteristics of the included patients, the morphological features of the aortic valve and aorta, the length of the left main coronary artery, and the laboratory findings (the coagulation and hematological parameters as well as the total cholesterol concentration were determined and compared with those of the tricuspid aortic valve (TAV patients. RESULTS: The BAV patients were younger than the TAV patients for a valve surgery in the last 3 months of the study period. The BAV patients were predominantly male. Most of the BAVs that were surgically treated were stenotic, regurgitant, or combined, and only 19 (7.88% were normally functioning valves. According to echocardiography or operative records, 148 (78.31% were type A, 31 (16.40% were type B, and 10 (5.29% were type C. The left main coronary artery was much shorter in the BAV patients than it was in the TAV patients. There was no significant difference between BAV and TAV patients in the total cholesterol concentrations; whereas differences were noted between patients receiving lipid-lowering therapy and those not receiving lipid-lowering therapy. The dimensions of the aortic root, sinotubular junction, and ascending aorta were beyond normal limits, while they were significantly smaller in the BAV patients than in the TAV patients. They were also much smaller in patients receiving statin therapy than those not receiving statin therapy in both groups. Moreover, the aortic dilation in the BAV group was found to be significantly associated with patient age. CONCLUSIONS: The BAV patients developed aortic wall and

The research on static bifurcation characteristics and parametric effect of two-phase natural circulation and passive system

International Nuclear Information System (INIS)

Xu Jijun; Yang Yanhua; Kuang Bo; Yao Wei; Zhang Ronghua; Tong Lili

2001-01-01

The formation of dissipative structures has long been known to occur in hydrodynamics. The two-phase natural circulation and passive system (TPNCPS) instability is a dissipative structure problem in multiphase hydrodynamics. The spectrum of the static bifurcation solutions (SBS) of TPNCPS through the variation of a parameter (one or more) has been derived in terms of Bifurcation Theory and DERPAR Numerical Method. Based on the appearance of Thermal-Siphon Hysteresis, the transport heat capability, static excursion criterion, stationary margin, transport heat capability of specific mass flow-rate and the disappear of bifurcation-the transition of single-valued region with the change of parameter have been defined. Such phenomena are the problems of describing self-organization, i.e. detailed study of stationary and/or time dependent status evolving with changes of characteristic parameter. A comparison between computational curves and low-pressure experimental data shows the tendency of evolutionary processes compatibly. The further tests are needed

Aortic root reimplantation procedure: a new milestone in aortic valve-sparing operations

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А. М. Чернявский

2016-08-01

Full Text Available Aim: Emphasis in this study was placed on clinical and functional assessment of a modified "Florida Sleeve" procedure during surgical correction of ascending aorta aneurysms with concomitant aortic insufficiency.Methods: 32 patients with an aneurysm of the ascending aorta and aortic insufficiency underwent a modified "Florida Sleeve" procedure. The average follow-up was 17 (0-60 months. The average age of patients was 57±13 (23-73 years 56±13 years.Results: The expected 4-year cumulative survival rate was 84.3%. Overall freedom from aortic insufficiency in the late period was 88.9%. Median aortic regurgitation was 1+ (1; 2. Long-term follow-up revealed no valve-associated complications.Conclusion: The aortic root reimplantation procedure enables optimal correction of the existing lesions of the aortic root without performing aortic valve replacement and demonstrates stable clinical and functional outcomes in the long-term period.Key words: aortic aneurysm; aortic valve; valve-sparing operations.FundingThe study had no sponsorship.Conflict of interestThe authors declare no conflict of interest.

Acute Type II Aortic Dissection with Severe Aortic Regurgitation and Chronic Descending Aortic Dissection in Pregnant Patient with Marfan Syndrome

OpenAIRE

Lee, Seok-Soo; Jung, Tae-Eun; Lee, Dong Hyup

2012-01-01

Aortic dilatation and dissection are severe complications during pregnancy that can be fatal to both the mother and the fetus. The risks of these complications are especially high in pregnant patients with Marfan syndrome; however, incidents of descending aortic dissection are very rare. This case report involves a successful Bentall procedure for and recovery from a rare aortic dissection in a pregnant Marfan patient who developed acute type II aortic dissection with severe aortic regurgitat...

Aortic valve replacement for aortic stenosis caused by alkaptonuria.

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Hiroyoshi, Junko; Saito, Aya; Panthee, Nirmal; Imai, Yasushi; Kawashima, Dai; Motomura, Noboru; Ono, Minoru

2013-03-01

We report a case of aortic stenosis associated with ochronosis in a 70-year-old man who underwent biologic aortic valve replacement. Intraoperative findings included ochronosis of a severely calcified pigmented aortic valve along with pigmentation of the intima of the aorta. Copyright © 2013 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.

Removal of self expandable metallic airway stent: A rare case report

OpenAIRE

Chawla, Rakesh K.; Madan, Arun; Singh, Ishwar; Mudoiya, Rahul; Chawla, Aditya; Gupta, Radha; Chawla, Kiran; Chhabra, Roopam

2013-01-01

Covered self expandable metallic airway stents (SEMS) have been used for benign tracheal stenosis, post intubation tracheal stenosis, tracheal burn or trauma, tracheo-broncho-malacia, and extrinsic compression of trachea. Their placement is considered to be permanent, with open surgery the only way to remove the stent, though there are few cases reports of their removal with the bronchoscope, but the complications after their removal are very high. In our patient, one and a half years after p...

Acute Aortic Arch Perforation During Transcatheter Aortic Valve Replacement in Bicuspid Aortic Stenosis and a Gothic Aortic Arch

DEFF Research Database (Denmark)

Millan-Iturbe, Oscar; Sawaya, Fadi J.; Bieliauskas, Gintautas

2017-01-01

AS because of its unique anatomic features. This case report describes an acute aortic perforation during delivery of a transcatheter heart valve to treat a severe bicuspid AS with a “gothic aortic arch”; more careful evaluation of the preprocedural multislice computed tomographic scan would have unveiled...

Comparison of visibility for four self-expanding nitinol bare stents in vitro

International Nuclear Information System (INIS)

Wiesinger, Benjamin; Stutz, Alexander; Schmehl, Joerg; Groezinger, Gerd; Claussen, Claus Detlef; Wiskirchen, Jakub

2012-01-01

Background Sufficient radiopacity of stents is a prerequisite for safe interventions and minimization of the radiation dose for the patient and the interventionist. Modern nitinol stents are considered less radiopaque compared to formerly used stents. Purpose To evaluate the objective detection rate (ODR) and the subjective radiopacity score (SRS) of four self-expanding nitinol stents with their markers on a phantom human pelvis. Material and Methods We evaluated the ODR (as a percentage of correctly identified stents) and the SRS (on a scale from 0 = not visible to 4 = excellent visibility) for four self-expanding nitinol stents (SinusSuperflex, SMART, Luminexx, Zilver) with 8 mm diameter and 40 mm length. Stents were placed on a phantom human pelvis and images of the stents were taken in four different positions (right and left lumbosacral joint and near the right and left limbus acetabuli) using the following modes: spotfilm, pulsed fluoroscopy (4, 7.5, 15, and 30 pulses/min) and at three different digital magnification modes. Dose area products (DAPs) were assessed. Results ODR and SRS, respectively, were significantly increased for the SMART stent compared to all other tested stents (P < 0.05): SMART 93.53% and 2.43, SinusSuperflex 90.81% and 2.21, Luminexx 90.39% and 2.20, and Zilver 89.28% and 2.21. ODR was significantly reduced in position 3 where the bone overlap was more pronounced for all stents (detection rates 77.14-79.56%). An increase in magnification significantly improved the ODR and SRS for all stents (70.33-99.25% and 1.07-3.28, respectively, P < 0.05). Increased pulsing frequency did not improve the ODR of the various stents but did increase the DAP. Conclusion The SMART stent had the best overall performance. In the presence of bone overlap, all self-expanding nitinol stents had poor results. Increased pulsing frequency did not improve ODR or SRS but did increase the DAP. Use of digital magnification modes had no effect on DAP increasing ODR

Stability and bifurcation analysis in a delayed SIR model

International Nuclear Information System (INIS)

Jiang Zhichao; Wei Junjie

2008-01-01

In this paper, a time-delayed SIR model with a nonlinear incidence rate is considered. The existence of Hopf bifurcations at the endemic equilibrium is established by analyzing the distribution of the characteristic values. A explicit algorithm for determining the direction of the Hopf bifurcation and the stability of the bifurcating periodic solutions are derived by using the normal form and the center manifold theory. Numerical simulations to support the analytical conclusions are carried out

Tratamento endovascular de ruptura traumática da aorta torácica descendente Endovascular treatment of traumatic descending thoracic aortic rupture

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João Roberto Breda

2007-06-01

Full Text Available Paciente do sexo feminino, 55 anos de idade, vítima de atropelamento, foi admitida em unidade de emergência, onde se realizou o diagnóstico clínico, radiológico e tomográfico de ruptura traumática da aorta torácica descendente. Diante do achado, a paciente foi encaminhada para tratamento endovascular com colocação de endoprótese auto-expansível (stent pela artéria femoral. O tratamento obteve sucesso, evidenciado pela exclusão da lesão localizada previamente no istmo aórtico. O tratamento endovascular tem sido indicado nas afecções de aorta torácica descendente com bons resultados iniciais. Na ruptura traumática de aorta, a terapêutica endovascular representa uma alternativa aceitável, especialmente devido aos riscos do tratamento operatório convencional.A 55-year-old, female patient who was run over by a motor vehicle was admitted at an emergency room. Clinical, radiological and tomographic diagnosis of traumatic descending aortic thoracic rupture was performed. The patient was referred for endovascular treatment with placement of a self-expandable stent through the femoral artery. Treatment was successful, with exclusion of the lesion previously located in the aortic isthmus. Endovascular treatment has been indicated in the treatment of descending thoracic aortic diseases, with good initial results. In case of traumatic aortic rupture, endovascular treatment is a feasible alternative, especially due to risks offered by the conventional surgical treatment.

Bifurcating fronts for the Taylor-Couette problem in infinite cylinders

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Hărăguş-Courcelle, M.; Schneider, G.

We show the existence of bifurcating fronts for the weakly unstable Taylor-Couette problem in an infinite cylinder. These fronts connect a stationary bifurcating pattern, here the Taylor vortices, with the trivial ground state, here the Couette flow. In order to show the existence result we improve a method which was already used in establishing the existence of bifurcating fronts for the Swift-Hohenberg equation by Collet and Eckmann, 1986, and by Eckmann and Wayne, 1991. The existence proof is based on spatial dynamics and center manifold theory. One of the difficulties in applying center manifold theory comes from an infinite number of eigenvalues on the imaginary axis for vanishing bifurcation parameter. But nevertheless, a finite dimensional reduction is possible, since the eigenvalues leave the imaginary axis with different velocities, if the bifurcation parameter is increased. In contrast to previous work we have to use normalform methods and a non-standard cut-off function to obtain a center manifold which is large enough to contain the bifurcating fronts.

Long-Term Health Benefit of Transcatheter Aortic Valve Replacement in Patients With Chronic Lung Disease.

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Crestanello, Juan A; Popma, Jeffrey J; Adams, David H; Deeb, G Michael; Mumtaz, Mubashir; George, Barry; Huang, Jian; Reardon, Michael J

2017-11-27

This study sought to characterize the long-term effect of chronic lung disease (CLD) on mortality, clinical outcomes, quality of life, and health benefits after transcatheter aortic valve replacement (TAVR) with a self-expanding bioprosthesis. The long-term effect of CLD after TAVR is unknown. Prevalence and severity of CLD was determined at baseline in high- and extreme-risk patients with aortic stenosis from the CoreValve US Pivotal Trial. Clinical outcomes and health status were assessed using the Kansas City Cardiomyopathy Questionnaire overall summary score (KCCQ-OS). A favorable health benefit was defined as alive with a KCCQ-OS ≥60 and stability (CLD was present in 55% (20% mild, 13% moderate, 22% severe) of the 1,030 patients studied. All-cause mortality was higher in patients with moderate and severe CLD at 1 year (19.6% mild, 28.1% moderate, 26.9% severe CLD vs. 19.2% non-CLD; p = 0.030) and 3 years (44.8% mild, 53.0% moderate, 51.9% severe vs. 37.7% non-CLD; p CLD at 1 and 3 years. All patients had a nearly 20-point improvement in KCCQ-OS at 1 and 3 years. However, only 43.3% of patients with CLD had a favorable health benefit at 1 year and 22.5% at 3 years. Moderate and severe CLD increases 1- and 3-year mortality after TAVR. Although functional status and quality of life were improved in CLD at 1 and 3 years after TAVR, a favorable health benefit was only achieved in selected patients. (Safety and Efficacy Study of the Medtronic CoreValve System in the Treatment of Symptomatic Severe Aortic Stenosis in High Risk and Very High Risk Subjects Who Need Aortic Valve Replacement; NCT01240902). Copyright © 2017 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

Secondary Channel Bifurcation Geometry: A Multi-dimensional Problem

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Gaeuman, D.; Stewart, R. L.

2017-12-01

The construction of secondary channels (or side channels) is a popular strategy for increasing aquatic habitat complexity in managed rivers. Such channels, however, frequently experience aggradation that prevents surface water from entering the side channels near their bifurcation points during periods of relatively low discharge. This failure to maintain an uninterrupted surface water connection with the main channel can reduce the habitat value of side channels for fish species that prefer lotic conditions. Various factors have been proposed as potential controls on the fate of side channels, including water surface slope differences between the main and secondary channels, the presence of main channel secondary circulation, transverse bed slopes, and bifurcation angle. A quantitative assessment of more than 50 natural and constructed secondary channels in the Trinity River of northern California indicates that bifurcations can assume a variety of configurations that are formed by different processes and whose longevity is governed by different sets of factors. Moreover, factors such as bifurcation angle and water surface slope vary with discharge level and are continuously distributed in space, such that they must be viewed as a multi-dimensional field rather than a single-valued attribute that can be assigned to a particular bifurcation.

Bifurcations of a periodically forced microbial continuous culture model with restrained growth rate

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Ren, Jingli; Yuan, Qigang

2017-08-01

A three dimensional microbial continuous culture model with a restrained microbial growth rate is studied in this paper. Two types of dilution rates are considered to investigate the dynamic behaviors of the model. For the unforced system, fold bifurcation and Hopf bifurcation are detected, and numerical simulations reveal that the system undergoes degenerate Hopf bifurcation. When the system is periodically forced, bifurcation diagrams for periodic solutions of period-one and period-two are given by researching the Poincaré map, corresponding to different bifurcation cases in the unforced system. Stable and unstable quasiperiodic solutions are obtained by Neimark-Sacker bifurcation with different parameter values. Periodic solutions of various periods can occur or disappear and even change their stability, when the Poincaré map of the forced system undergoes Neimark-Sacker bifurcation, flip bifurcation, and fold bifurcation. Chaotic attractors generated by a cascade of period doublings and some phase portraits are given at last.

An upper limit for slow-earthquake zones: self-oscillatory behavior through the Hopf bifurcation mechanism from a spring-block model under lubricated surfaces

Science.gov (United States)

Castellanos-Rodríguez, Valentina; Campos-Cantón, Eric; Barboza-Gudiño, Rafael; Femat, Ricardo

2017-08-01

The complex oscillatory behavior of a spring-block model is analyzed via the Hopf bifurcation mechanism. The mathematical spring-block model includes Dieterich-Ruina's friction law and Stribeck's effect. The existence of self-sustained oscillations in the transition zone - where slow earthquakes are generated within the frictionally unstable region - is determined. An upper limit for this region is proposed as a function of seismic parameters and frictional coefficients which are concerned with presence of fluids in the system. The importance of the characteristic length scale L, the implications of fluids, and the effects of external perturbations in the complex dynamic oscillatory behavior, as well as in the stationary solution, are take into consideration.

The use of transcatheter aortic valve replacement vs surgical aortic valve replacement for the treatment of aortic stenosis

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Jensen HA

2015-08-01

Full Text Available Hanna A Jensen, Lillian L Tsai, Vinod H Thourani Division of Cardiothoracic Surgery, Joseph B Whitehead Department of Surgery, Structural Heart and Valve Center, Emory University School of Medicine, Atlanta, GA, USA Abstract: Severe aortic stenosis (AS is associated with considerable morbidity and mortality and is increasing in prevalence as the global population increases. Since AS primarily affects the elderly, many of these patients have comorbidities that make them poor candidates for the gold standard treatment for AS, surgical aortic valve replacement. Transcatheter aortic valve replacement has emerged as a novel technology for the management of AS in higher risk patients over the past decade. Randomized trials have established the safety and efficacy of transcatheter aortic valve replacement, and the medical community has rallied to identify the patients who are most suitable for this transformative treatment. This review focuses on outlining the key procedural differences, describing the unique challenges of both operations, and finally assessing and comparing outcomes both on a general level and in challenging patient subgroups. Keywords: aortic valve replacement, transcatheter aortic valve replacement, surgical aortic valve replacement 

Bifurcation dynamics of the tempered fractional Langevin equation

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Zeng, Caibin, E-mail: macbzeng@scut.edu.cn; Yang, Qigui, E-mail: qgyang@scut.edu.cn [School of Mathematics, South China University of Technology, Guangzhou 510640 (China); Chen, YangQuan, E-mail: ychen53@ucmerced.edu [MESA LAB, School of Engineering, University of California, Merced, 5200 N. Lake Road, Merced, California 95343 (United States)

2016-08-15

Tempered fractional processes offer a useful extension for turbulence to include low frequencies. In this paper, we investigate the stochastic phenomenological bifurcation, or stochastic P-bifurcation, of the Langevin equation perturbed by tempered fractional Brownian motion. However, most standard tools from the well-studied framework of random dynamical systems cannot be applied to systems driven by non-Markovian noise, so it is desirable to construct possible approaches in a non-Markovian framework. We first derive the spectral density function of the considered system based on the generalized Parseval's formula and the Wiener-Khinchin theorem. Then we show that it enjoys interesting and diverse bifurcation phenomena exchanging between or among explosive-like, unimodal, and bimodal kurtosis. Therefore, our procedures in this paper are not merely comparable in scope to the existing theory of Markovian systems but also provide a possible approach to discern P-bifurcation dynamics in the non-Markovian settings.

Altered aortic shape in bicuspid aortic valve relatives influences blood flow patterns.

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Schnell, Susanne; Smith, Danielle A; Barker, Alex J; Entezari, Pegah; Honarmand, Amir R; Carr, Maria L; Malaisrie, S Chris; McCarthy, Patrick M; Collins, Jeremy; Carr, James C; Markl, Michael

2016-11-01

Bicuspid aortic valve (BAV) is known to exhibit familial inheritance and is associated with aortopathy and altered aortic haemodynamics. However, it remains unclear whether BAV-related aortopathy can be inherited independently of valve morphology. Four-dimensional flow magnetic resonance imaging for the in vivo assessment of thoracic aortic 3D blood flow was performed in 24 BAV relatives with trileaflet aortic valves (age = 40 ± 14 years) and 15 healthy controls (age = 37 ± 10 years). Data analysis included aortic dimensions, shape (round/gothic/cubic), and 3D blood flow characteristics (semi-quantitative vortex/helix grading and peak velocities). Cubic and gothic aortic shapes were markedly more prevalent in BAV relatives compared with controls (38 vs. 7%). Ascending aorta (AAo) vortex flow in BAV relatives was significantly increased compared with controls (grading = 1.5 ± 1.0 vs. 0.6 ± 0.9, P = 0.015). Aortic haemodynamics were influenced by aortic shape: peak velocities were reduced for gothic aortas vs. round aortas (P = 0.003); vortex flow was increased for cubic aortas in the AAo (P gothic aortas in the AAo and descending aorta (P = 0.003, P = 0.029). Logistic regression demonstrated significant associations of shape with severity of vortex flow in AAo (P < 0.001) and aortic arch (P = 0.016) in BAV relatives. BAV relatives expressed altered aortic shape and increased vortex flow despite the absence of valvular disease or aortic dilatation. These data suggest a heritable component of BAV-related aortopathy affecting aortic shape and aberrant blood flow, independent of valve morphology. Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2016. For permissions please email: journals.permissions@oup.com.

A note on tilted Bianchi type VIh models: the type III bifurcation

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Coley, A. A.; Hervik, S.

2008-10-01

In this note we complete the analysis of Hervik, van den Hoogen, Lim and Coley (2007 Class. Quantum Grav. 24 3859) of the late-time behaviour of tilted perfect fluid Bianchi type III models. We consider models with dust, and perfect fluids stiffer than dust, and eludicate the late-time behaviour by studying the centre manifold which dominates the behaviour of the model at late times. In the dust case, this centre manifold is three-dimensional and can be considered a double bifurcation as the two parameters (h and γ) of the type VIh model are varied. We therefore complete the analysis of the late-time behaviour of tilted ever-expanding Bianchi models of types I VIII.

Hybrid Repair of Complex Thoracic Aortic Arch Pathology: Long-Term Outcomes of Extra-anatomic Bypass Grafting of the Supra-aortic Trunk

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Lotfi, S., E-mail: shamim.lotfi@kcl.ac.uk; Clough, R. E.; Ali, T. [Guy' s and St. Thomas' NHS Trust, Vascular Surgery (United Kingdom); Salter, R. [Guy' s and St. Thomas' NHS Trust, Interventional Radiology (United Kingdom); Young, C. P. [Guy' s and St. Thomas' NHS Trust, Cardiac Surgery (United Kingdom); Bell, R.; Modarai, B.; Taylor, P., E-mail: peter.taylor@gstt.nhs.uk [Guy' s and St. Thomas' NHS Trust, Vascular Surgery (United Kingdom)

2013-02-15

Hybrid repair constitutes supra-aortic debranching before thoracic endovascular aortic repair (TEVAR). It offers improved short-term outcome compared with open surgery; however, longer-term studies are required to assess patient outcomes and patency of the extra-anatomic bypass grafts. A prospectively maintained database of 380 elective and urgent patients who had undergone TEVAR (1997-2011) was analyzed retrospectively. Fifty-one patients (34 males; 17 females) underwent hybrid repair. Median age was 71 (range, 18-90) years with mean follow-up of 15 (range, 0-61) months. Perioperative complications included death: 10 % (5/51), stroke: 12 % (6/51), paraplegia: 6 % (3/51), endoleak: 16 % (8/51), rupture: 4 % (2/51), upper-limb ischemia: 2 % (1/51), bypass graft occlusion: 4 % (2/51), and cardiopulmonary complications in 14 % (7/51). Three patients (6 %) required emergency intervention for retrograde dissection: (2 aortic root repairs; 2 innominate stents). Early reintervention was performed for type 1 endoleak in two patients (2 proximal cuff extensions). One patient underwent innominate stenting and revision of their bypass for symptomatic restenosis. At 48 months, survival was 73 %. Endoleak was detected in three (6 %) patients (type 1 = 2; type 2 = 1) requiring debranching with proximal stent graft (n = 2) and proximal extension cuff (n = 1). One patient had a fatal rupture of a mycotic aneurysm and two arch aneurysms expanded. No bypass graft occluded after the perioperative period. Hybrid operations to treat aortic arch disease can be performed with results comparable to open surgery. The longer-term outcomes demonstrate low rates of reintervention and high rates of graft patency.

Hybrid Repair of Complex Thoracic Aortic Arch Pathology: Long-Term Outcomes of Extra-anatomic Bypass Grafting of the Supra-aortic Trunk

International Nuclear Information System (INIS)

Lotfi, S.; Clough, R. E.; Ali, T.; Salter, R.; Young, C. P.; Bell, R.; Modarai, B.; Taylor, P.

2013-01-01

Hybrid repair constitutes supra-aortic debranching before thoracic endovascular aortic repair (TEVAR). It offers improved short-term outcome compared with open surgery; however, longer-term studies are required to assess patient outcomes and patency of the extra-anatomic bypass grafts. A prospectively maintained database of 380 elective and urgent patients who had undergone TEVAR (1997–2011) was analyzed retrospectively. Fifty-one patients (34 males; 17 females) underwent hybrid repair. Median age was 71 (range, 18–90) years with mean follow-up of 15 (range, 0–61) months. Perioperative complications included death: 10 % (5/51), stroke: 12 % (6/51), paraplegia: 6 % (3/51), endoleak: 16 % (8/51), rupture: 4 % (2/51), upper-limb ischemia: 2 % (1/51), bypass graft occlusion: 4 % (2/51), and cardiopulmonary complications in 14 % (7/51). Three patients (6 %) required emergency intervention for retrograde dissection: (2 aortic root repairs; 2 innominate stents). Early reintervention was performed for type 1 endoleak in two patients (2 proximal cuff extensions). One patient underwent innominate stenting and revision of their bypass for symptomatic restenosis. At 48 months, survival was 73 %. Endoleak was detected in three (6 %) patients (type 1 = 2; type 2 = 1) requiring debranching with proximal stent graft (n = 2) and proximal extension cuff (n = 1). One patient had a fatal rupture of a mycotic aneurysm and two arch aneurysms expanded. No bypass graft occluded after the perioperative period. Hybrid operations to treat aortic arch disease can be performed with results comparable to open surgery. The longer-term outcomes demonstrate low rates of reintervention and high rates of graft patency.

Bifurcation of learning and structure formation in neuronal maps

DEFF Research Database (Denmark)

Marschler, Christian; Faust-Ellsässer, Carmen; Starke, Jens

2014-01-01

to map formation in the laminar nucleus of the barn owl's auditory system. Using equation-free methods, we perform a bifurcation analysis of spatio-temporal structure formation in the associated synaptic-weight matrix. This enables us to analyze learning as a bifurcation process and follow the unstable...... states as well. A simple time translation of the learning window function shifts the bifurcation point of structure formation and goes along with traveling waves in the map, without changing the animal's sound localization performance....

An Extensive Stanford Type A Aortic Dissection Involving Bilateral Carotid and Iliac Arteries

Directory of Open Access Journals (Sweden)

E. W. Lee

2013-01-01

Full Text Available We present a rare case of continuous, extensive aortic dissection (AD involving the bilateral common carotid arteries, the ascending, thoracic, and abdominal aorta, and bifurcation of the right common iliac artery. A 61-year-old man with history of chronic hypertension presented with a one-day history of chest pain, vertigo, left facial drooping, and left hemiparesis. Despite the presence of bilateral carotid bruits, doppler ultrasound of the neck was postponed, and the patient was treated with thrombolytic therapy for a presumed ischemic stroke. The patient's symptoms began to resolve within an hour of treatment, at which time treatment was withheld. Ultrasound performed the following day showed dissection of bilateral common carotid arteries, and CT angiography demonstrated extensive AD as described earlier. The patient subsequently underwent cardiovascular surgery and has been doing clinically well since then. AD has a myriad of manifestations depending on the involvement of aortic branches. Our paper illustrates the importance of having a high index of suspicion for AD when a patient presents with a picture of ischemic stroke, since overlapping signs and symptoms exist between AD and stroke. Differentiating between the two conditions is central to patient care as thrombolytic therapy can be helpful in stroke, but detrimental in AD.

Hopf bifurcation in a delayed reaction-diffusion-advection population model

Science.gov (United States)

Chen, Shanshan; Lou, Yuan; Wei, Junjie

2018-04-01

In this paper, we investigate a reaction-diffusion-advection model with time delay effect. The stability/instability of the spatially nonhomogeneous positive steady state and the associated Hopf bifurcation are investigated when the given parameter of the model is near the principle eigenvalue of an elliptic operator. Our results imply that time delay can make the spatially nonhomogeneous positive steady state unstable for a reaction-diffusion-advection model, and the model can exhibit oscillatory pattern through Hopf bifurcation. The effect of advection on Hopf bifurcation values is also considered, and our results suggest that Hopf bifurcation is more likely to occur when the advection rate increases.

Bifurcation of rupture path by linear and cubic damping force

Science.gov (United States)

Dennis L. C., C.; Chew X., Y.; Lee Y., C.

2014-06-01

Bifurcation of rupture path is studied for the effect of linear and cubic damping. Momentum equation with Rayleigh factor was transformed into ordinary differential form. Bernoulli differential equation was obtained and solved by the separation of variables. Analytical or exact solutions yielded the bifurcation was visible at imaginary part when the wave was non dispersive. For the dispersive wave, bifurcation of rupture path was invisible.

Long-Term Risk for Aortic Complications After Aortic Valve Replacement in Patients With Bicuspid Aortic Valve Versus Marfan Syndrome.

Science.gov (United States)

Itagaki, Shinobu; Chikwe, Joanna P; Chiang, Yuting P; Egorova, Natalia N; Adams, David H

2015-06-09

Bicuspid aortic valves are associated with valve dysfunction, ascending aortic aneurysm and dissection. Management of the ascending aorta at the time of aortic valve replacement (AVR) in these patients is controversial and has been extrapolated from experience with Marfan syndrome, despite the absence of comparative long-term outcome data. This study sought to assess whether the natural history of thoracic aortopathy after AVR in patients with bicuspid aortic valve disease is substantially different from that seen in patients with Marfan syndrome. In this retrospective comparison, outcomes of 13,205 adults (2,079 with bicuspid aortic valves, 73 with Marfan syndrome, and 11,053 control patients with acquired aortic valve disease) who underwent primary AVR without replacement of the ascending aorta in New York State between 1995 and 2010 were compared. The median follow-up time was 6.6 years. The long-term incidence of thoracic aortic dissection was significantly higher in patients with Marfan syndrome (5.5 ± 2.7%) compared with those with bicuspid valves (0.55 ± 0.21%) and control group patients (0.41 ± 0.08%, p Marfan syndrome (10.8 ± 4.4%) compared with those with bicuspid valves (4.8 ± 0.8%) and control group patients (1.4 ± 0.2%) (p Marfan syndrome were significantly more likely to undergo thoracic aortic surgery in late follow-up (10.4 ± 4.3%) compared with those with bicuspid valves (2.5 ± 0.6%) and control group patients (0.50 ± 0.09%) (p Marfan syndrome compared with those with bicuspid aortic valves confirm that operative management of patients with bicuspid aortic valves should not be extrapolated from Marfan syndrome and support discrete treatment algorithms for these different clinical entities. Copyright © 2015 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

Square-lattice random Potts model: criticality and pitchfork bifurcation

International Nuclear Information System (INIS)

Costa, U.M.S.; Tsallis, C.

1983-01-01

Within a real space renormalization group framework based on self-dual clusters, the criticality of the quenched bond-mixed q-state Potts ferromagnet on square lattice is discussed. On qualitative grounds it is exhibited that the crossover from the pure fixed point to the random one occurs, while q increases, through a pitchfork bifurcation; the relationship with Harris criterion is analyzed. On quantitative grounds high precision numerical values are presented for the critical temperatures corresponding to various concentrations of the coupling constants J 1 and J 2 , and various ratios J 1 /J 2 . The pure, random and crossover critical exponents are discussed as well. (Author) [pt

Outcome of self-expanding metal stenting followed by radiation therapy for unresectable extrahepatic bile duct cancer

International Nuclear Information System (INIS)

Jin Jing; Gao Li; Yu Zihao; Han Jianzhu; Zhai Renyou

2007-01-01

Objective: To retrospectively analyze the efficacy for self-expanding metal stenting followed by radiation therapy for unresectable extrahepatic bile duct cancer. Methods: From Jan 1996 to Sep 2002, 17 patients were treated with self-expanding metal stenting followed by Ir 192 high dose brachytherapy (brachytherapy group, n=5)and by external beam radiation therapy(external radiation therapy group, n=9). Brachytherapy was delivered on the same day or the following day after stenting with the total dose of DT 20- 30 Gy, twice daily, for 2-3 days. The median total dosage of external radiation therapy was 48 Gy (14-66 Gy), 2 Gy/fraction. Results: Jaundice was released after metal stenting from 71.4% to 14.3% (P=0.001), showing no significant difference between brachytherapy and external radiation therapy in terms of jaundice release(χ 2 =0.21, P=0.65). The median survival period(5-35 months)for whole groups was 12 months 1-, 2-year survival rates were 40.8% and 8.16%, respectively. No significant difference was shown for patients received either brachytherapy or external radiation therapy for 8 months, but with 1,2 year survival rate as 40.0%, 13.3%, respectively (χ 2 =1.10, P=0.29). Conclusions: Self-expanding metal stenting is able to release jaundice significantly and followed by high dose radiation therapy may further prolong the survival. (authors)

Bifurcation structures of a cobweb model with memory and competing technologies

Science.gov (United States)

Agliari, Anna; Naimzada, Ahmad; Pecora, Nicolò

2018-05-01

In this paper we study a simple model based on the cobweb demand-supply framework with costly innovators and free imitators. The evolutionary selection between technologies depends on a performance measure which is related to the degree of memory. The resulting dynamics is described by a two-dimensional map. The map has a fixed point which may lose stability either via supercritical Neimark-Sacker bifurcation or flip bifurcation and several multistability situations exist. We describe some sequences of global bifurcations involving attracting and repelling closed invariant curves. These bifurcations, characterized by the creation of homoclinic connections or homoclinic tangles, are described through several numerical simulations. Particular bifurcation phenomena are also observed when the parameters are selected inside a periodicity region.

Analysis of stability and Hopf bifurcation for a delayed logistic equation

International Nuclear Information System (INIS)

Sun Chengjun; Han Maoan; Lin Yiping

2007-01-01

The dynamics of a logistic equation with discrete delay are investigated, together with the local and global stability of the equilibria. In particular, the conditions under which a sequence of Hopf bifurcations occur at the positive equilibrium are obtained. Explicit algorithm for determining the stability of the bifurcating periodic solutions and the direction of the Hopf bifurcation are derived by using the theory of normal form and center manifold [Hassard B, Kazarino D, Wan Y. Theory and applications of Hopf bifurcation. Cambridge: Cambridge University Press; 1981.]. Global existence of periodic solutions is also established by using a global Hopf bifurcation result of Wu [Symmetric functional differential equations and neural networks with memory. Trans Amer Math Soc 350:1998;4799-38.

Bifurcation of Jovian magnetotail current sheet

Directory of Open Access Journals (Sweden)

P. L. Israelevich

2006-07-01

Full Text Available Multiple crossings of the magnetotail current sheet by a single spacecraft give the possibility to distinguish between two types of electric current density distribution: single-peaked (Harris type current layer and double-peaked (bifurcated current sheet. Magnetic field measurements in the Jovian magnetic tail by Voyager-2 reveal bifurcation of the tail current sheet. The electric current density possesses a minimum at the point of the Bx-component reversal and two maxima at the distance where the magnetic field strength reaches 50% of its value in the tail lobe.

Discretizing the transcritical and pitchfork bifurcations – conjugacy results

KAUST Repository

Ló czi, Lajos

2015-01-01

© 2015 Taylor & Francis. We present two case studies in one-dimensional dynamics concerning the discretization of transcritical (TC) and pitchfork (PF) bifurcations. In the vicinity of a TC or PF bifurcation point and under some natural assumptions

Shells, orbit bifurcations, and symmetry restorations in Fermi systems

Energy Technology Data Exchange (ETDEWEB)

Magner, A. G., E-mail: magner@kinr.kiev.ua; Koliesnik, M. V. [NASU, Institute for Nuclear Research (Ukraine); Arita, K. [Nagoya Institute of Technology, Department of Physics (Japan)

2016-11-15

The periodic-orbit theory based on the improved stationary-phase method within the phase-space path integral approach is presented for the semiclassical description of the nuclear shell structure, concerning themain topics of the fruitful activity ofV.G. Soloviev. We apply this theory to study bifurcations and symmetry breaking phenomena in a radial power-law potential which is close to the realistic Woods–Saxon one up to about the Fermi energy. Using the realistic parametrization of nuclear shapes we explain the origin of the double-humped fission barrier and the asymmetry in the fission isomer shapes by the bifurcations of periodic orbits. The semiclassical origin of the oblate–prolate shape asymmetry and tetrahedral shapes is also suggested within the improved periodic-orbit approach. The enhancement of shell structures at some surface diffuseness and deformation parameters of such shapes are explained by existence of the simple local bifurcations and new non-local bridge-orbit bifurcations in integrable and partially integrable Fermi-systems. We obtained good agreement between the semiclassical and quantum shell-structure components of the level density and energy for several surface diffuseness and deformation parameters of the potentials, including their symmetry breaking and bifurcation values.

CISM Session on Bifurcation and Stability of Dissipative Systems

CERN Document Server

1993-01-01

The first theme concerns the plastic buckling of structures in the spirit of Hill’s classical approach. Non-bifurcation and stability criteria are introduced and post-bifurcation analysis performed by asymptotic development method in relation with Hutchinson’s work. Some recent results on the generalized standard model are given and their connection to Hill’s general formulation is presented. Instability phenomena of inelastic flow processes such as strain localization and necking are discussed. The second theme concerns stability and bifurcation problems in internally damaged or cracked colids. In brittle fracture or brittle damage, the evolution law of crack lengths or damage parameters is time-independent like in plasticity and leads to a similar mathematical description of the quasi-static evolution. Stability and non-bifurcation criteria in the sense of Hill can be again obtained from the discussion of the rate response.

Bifurcation of elastic solids with sliding interfaces

Science.gov (United States)

Bigoni, D.; Bordignon, N.; Piccolroaz, A.; Stupkiewicz, S.

2018-01-01

Lubricated sliding contact between soft solids is an interesting topic in biomechanics and for the design of small-scale engineering devices. As a model of this mechanical set-up, two elastic nonlinear solids are considered jointed through a frictionless and bilateral surface, so that continuity of the normal component of the Cauchy traction holds across the surface, but the tangential component is null. Moreover, the displacement can develop only in a way that the bodies in contact do neither detach, nor overlap. Surprisingly, this finite strain problem has not been correctly formulated until now, so this formulation is the objective of the present paper. The incremental equations are shown to be non-trivial and different from previously (and erroneously) employed conditions. In particular, an exclusion condition for bifurcation is derived to show that previous formulations based on frictionless contact or `spring-type' interfacial conditions are not able to predict bifurcations in tension, while experiments-one of which, ad hoc designed, is reported-show that these bifurcations are a reality and become possible when the correct sliding interface model is used. The presented results introduce a methodology for the determination of bifurcations and instabilities occurring during lubricated sliding between soft bodies in contact.

Bifurcations and degenerate periodic points in a three dimensional chaotic fluid flow

International Nuclear Information System (INIS)

Smith, L. D.; Rudman, M.; Lester, D. R.; Metcalfe, G.

2016-01-01

Analysis of the periodic points of a conservative periodic dynamical system uncovers the basic kinematic structure of the transport dynamics and identifies regions of local stability or chaos. While elliptic and hyperbolic points typically govern such behaviour in 3D systems, degenerate (parabolic) points also play an important role. These points represent a bifurcation in local stability and Lagrangian topology. In this study, we consider the ramifications of the two types of degenerate periodic points that occur in a model 3D fluid flow. (1) Period-tripling bifurcations occur when the local rotation angle associated with elliptic points is reversed, creating a reversal in the orientation of associated Lagrangian structures. Even though a single unstable point is created, the bifurcation in local stability has a large influence on local transport and the global arrangement of manifolds as the unstable degenerate point has three stable and three unstable directions, similar to hyperbolic points, and occurs at the intersection of three hyperbolic periodic lines. The presence of period-tripling bifurcation points indicates regions of both chaos and confinement, with the extent of each depending on the nature of the associated manifold intersections. (2) The second type of bifurcation occurs when periodic lines become tangent to local or global invariant surfaces. This bifurcation creates both saddle–centre bifurcations which can create both chaotic and stable regions, and period-doubling bifurcations which are a common route to chaos in 2D systems. We provide conditions for the occurrence of these tangent bifurcations in 3D conservative systems, as well as constraints on the possible types of tangent bifurcation that can occur based on topological considerations.

Bifurcation analysis and stability design for aircraft longitudinal motion with high angle of attack

Directory of Open Access Journals (Sweden)

Xin Qi

2015-02-01

Full Text Available Bifurcation analysis and stability design for aircraft longitudinal motion are investigated when the nonlinearity in flight dynamics takes place severely at high angle of attack regime. To predict the special nonlinear flight phenomena, bifurcation theory and continuation method are employed to systematically analyze the nonlinear motions. With the refinement of the flight dynamics for F-8 Crusader longitudinal motion, a framework is derived to identify the stationary bifurcation and dynamic bifurcation for high-dimensional system. Case study shows that the F-8 longitudinal motion undergoes saddle node bifurcation, Hopf bifurcation, Zero-Hopf bifurcation and branch point bifurcation under certain conditions. Moreover, the Hopf bifurcation renders series of multiple frequency pitch oscillation phenomena, which deteriorate the flight control stability severely. To relieve the adverse effects of these phenomena, a stabilization control based on gain scheduling and polynomial fitting for F-8 longitudinal motion is presented to enlarge the flight envelope. Simulation results validate the effectiveness of the proposed scheme.

A novel self-expanding fully retrievable intracranial stent (SOLO): experience in nine procedures of stent-assisted aneurysm coil occlusion

International Nuclear Information System (INIS)

Liebig, Thomas; Henkes, Hans; Reinartz, Joerg; Miloslavski, Elina; Kuehne, Dietmar

2006-01-01

The endovascular treatment of large and broad-necked aneurysms may require the use of a remodelling balloon or a stent system to achieve proper occlusion while maintaining the patency of the parent vessel. With the advent of self-expanding stents that can be delivered through a microcatheter, this kind of treatment has improved and problems with the previously used balloon expandable stents have largely been overcome. However, rigidity, insufficient trackability, and limited or non-existent retrievability may still restrict the application of self-expanding stents in some situations. Recently, a stent system with a new and different design has been introduced. This stent is highly flexible, fully retrievable, and can be delivered through a standard 0.021-inch microcatheter without a wire. We describe the first nine cases of stent-assisted coil occlusion of intracranial aneurysms with the use of this stent system. Between May and June of 2004, nine patients with large or broad-necked aneurysms were treated in two endovascular centres. The anatomy of the aneurysms and parent vessels, technical details of the procedure, performance of the stent system, and follow-up results were evaluated. In all procedures, the SOLO stent could be introduced without difficulty, in one procedure after positioning of a different self-expanding stent system had failed due to vessel tortuosity. Overlapping stents were placed in one patient and stent retrieval or repositioning was successfully performed in two procedures. There was no interference or limitation of subsequent coil occlusion after stenting. With regard to the stent, immediate postprocedure and follow-up angiograms were unremarkable in terms of thromboembolic events and signs of intimal hyperplasia. From our experience, we conclude that the SOLO stent shows satisfactory performance overall. Its unique design gives the stent properties that may help overcome some of the difficulties experienced with other self-expanding

Early Results of the PETTICOAT Technique for the Management of Acute Type A Aortic Dissection.

Science.gov (United States)

Kotha, Vamshi Krishna; Pozeg, Zlatko I; Herget, Eric J; Moon, Michael C; Appoo, Jehangir J

2017-08-01

Conventional surgical techniques for acute Type A aortic dissection (ATAAD) generally fail to address residual dissection in the descending aorta. The persistence of a false lumen is associated with visceral malperfusion in the acute setting and adverse aortic remodeling in the chronic setting. Hybrid aortic arch repair techniques may improve perioperative and long-term mortality by expanding the true lumen and obliterating the false lumen. However, there is a limit to the extent of aortic coverage due to the concomitant risk of spinal cord ischemia. In Type B dissection, the PETTICOAT (Provisional Extension To Induce Complete Attachment) technique, which entails stent graft coverage of the primary intimal tear followed by bare metal stent placement distally, may improve true lumen caliber and promote false lumen thrombosis without increasing the risk of spinal cord ischemia, as intercostal branches remain perfused through the bare metal stents. The technique of hybrid arch with surgical creation of a Dacron landing zone covering a stent graft in the proximal descending aorta and bare metal stents in the thoraco-abdominal aorta is a promising concept in the treatment of ATAAD.

Bifurcations of heterodimensional cycles with two saddle points

Energy Technology Data Exchange (ETDEWEB)

Geng Fengjie [School of Information Technology, China University of Geosciences (Beijing), Beijing 100083 (China)], E-mail: gengfengjie_hbu@163.com; Zhu Deming [Department of Mathematics, East China Normal University, Shanghai 200062 (China)], E-mail: dmzhu@math.ecnu.edu.cn; Xu Yancong [Department of Mathematics, East China Normal University, Shanghai 200062 (China)], E-mail: yancongx@163.com

2009-03-15

The bifurcations of 2-point heterodimensional cycles are investigated in this paper. Under some generic conditions, we establish the existence of one homoclinic loop, one periodic orbit, two periodic orbits, one 2-fold periodic orbit, and the coexistence of one periodic orbit and heteroclinic loop. Some bifurcation patterns different to the case of non-heterodimensional heteroclinic cycles are revealed.

Bifurcations of heterodimensional cycles with two saddle points

International Nuclear Information System (INIS)

Geng Fengjie; Zhu Deming; Xu Yancong

2009-01-01

The bifurcations of 2-point heterodimensional cycles are investigated in this paper. Under some generic conditions, we establish the existence of one homoclinic loop, one periodic orbit, two periodic orbits, one 2-fold periodic orbit, and the coexistence of one periodic orbit and heteroclinic loop. Some bifurcation patterns different to the case of non-heterodimensional heteroclinic cycles are revealed.

Suprarenal fixation resulting in intestinal malperfusion after endovascular aortic aneurysm repair.

Science.gov (United States)

Siani, Andrea; Accrocca, Federico; De Vivo, Gennaro; Marcucci, Giustino

2016-05-01

Superior mesenteric artery (SMA) and coeliac axis (CA) occlusion after endovascular abdominal aneurysm aortic repair (EVAR-AAA), using endograft with suprarenal fixation, are uncommon. However, we are reporting a case of visceral malperfusion, which occurred 7 days after successful EVAR with suprarenal fixation for symptomatic AAA. Endograft metal stent barbs caused severe stenosis of SMA and CA. A successful recovery of SMA was carried out by means of a balloon-expandable stent released through bare metal stent barbs. We believe that an unfavourable anatomy of a proximal aortic neck and visceral aorta may have caused a wrong stent strut deployment with the coverage of CA and SMA. © The Author 2016. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.

Membranous obstruction of inferior vena cava(MOIVC): treatment with percutaneous transluminal angioplasty(PTA) and self expandable metallic stent

Energy Technology Data Exchange (ETDEWEB)

Lee, Ki Yeol; Kim, Baek Hyun; Cha, In Ho; Lee, Nam Joon; Kim, Yun Hwan; Kim, Jung Hyuk [College of Medicine, Korea University, Seoul (Korea, Republic of)

1994-03-15

Percutaneous transluminal angioplasty(PTA) with a balloon catheter is a standard method of treatment for membranous obstruction of inferior vena cava(MOIVC). But, correct therapeutic approach has not been established for MOIVC patients whose lesion is associated with extensive thrombotic IVC occlusion. We tried to treat MOIVC associated with or without thrombus. We treated 13 cases of MOIVC(associated with thrombus in 7 cases, no thrombus in 6 cases) with PTA, thrombolysis and self-expandable metallic stents. PTA was successful in 8 cases, but failed in 5 cases. The recurred cases were retreated with PTA, but follow-up study revealed recoiling restenosis in 4 cases and intimal hyperplasia in 1 case at previous PTA site which could be overcome with a self-expandable metallic stent. The complication were occurred in 3 cases which were hemothorax, hemopericardium, and hemoperitoneum respectively. However, those were resolved by conservative treatment only. Recanalization and dilatation could be done in MOIVC patients with or without thrombosis for improvement of patient's symptom. Gianturco self-expandable metallic stent is useful in treatment of recurred MOIVC after balloon dilatation and preventing reocclusion of the IVC after PTA.

Self-expandable metal stents for malignant gastric outlet obstruction: A pooled analysis of prospective literature

NARCIS (Netherlands)

van Halsema, Emo E.; Rauws, Erik A. J.; Fockens, Paul; van Hooft, Jeanin E.

2015-01-01

To provide an overview of the clinical outcomes of self-expandable metal stent (SEMS) placement for malignant gastric outlet obstruction (MGOO). A systematic literature search was performed in PubMed of the literature published between January 2009 and March 2015. Only prospective studies that

Emergence of the bifurcation structure of a Langmuir–Blodgett transfer model

KAUST Repository

Köpf, Michael H

2014-10-07

© 2014 IOP Publishing Ltd & London Mathematical Society. We explore the bifurcation structure of a modified Cahn-Hilliard equation that describes a system that may undergo a first-order phase transition and is kept permanently out of equilibrium by a lateral driving. This forms a simple model, e.g., for the deposition of stripe patterns of different phases of surfactant molecules through Langmuir-Blodgett transfer. Employing continuation techniques the bifurcation structure is numerically investigated using the non-dimensional transfer velocity as the main control parameter. It is found that the snaking structure of steady front states is intertwined with a large number of branches of time-periodic solutions that emerge from Hopf or period-doubling bifurcations and end in global bifurcations (sniper and homoclinic). Overall the bifurcation diagram has a harp-like appearance. This is complemented by a two-parameter study in non-dimensional transfer velocity and domain size (as a measure of the distance to the phase transition threshold) that elucidates through which local and global codimension 2 bifurcations the entire harp-like structure emerges.

Sediment discharge division at two tidally influenced river bifurcations

NARCIS (Netherlands)

Sassi, M.G.; Hoitink, A.J.F.; Vermeulen, B.; Hidayat, H.

2013-01-01

[1] We characterize and quantify the sediment discharge division at two tidally influenced river bifurcations in response to mean flow and secondary circulation by employing a boat-mounted acoustic Doppler current profiler (ADCP), to survey transects at bifurcating branches during a semidiurnal

Self-expanding oesophageal metal stents for the palliation of dysphagia due to extrinsic compression

Energy Technology Data Exchange (ETDEWEB)

Gupta, N.K.; Boylan, C.E.; Razzaq, R.; England, R.E.; Mirra, L.; Martin, D.F. [Dept. of Radiology, South Manchester University Hospitals NHS Trust, Withington Hospital (United Kingdom)

1999-07-01

The role of self-expanding metallic stents is well established in the palliation of oesophageal stenosis and dysphagia due to primary oesophageal malignancy. However, their role in palliation of dysphagia due to external compressive mediastinal malignancies is not well established. The purpose of this study was to assess the efficacy of self-expanding metallic stents in the palliation of dysphagia due to extrinsic oesophageal compression by mediastinal malignancy. Between January 1995 and January 1998, 21 patients with oesophageal compression due to malignant mediastinal tumours underwent oesophageal stent placement for palliation of dysphagia. Complete data were available in 17 patients (10 men and 7 women). The mean age was 63.5 years (range 46-89 years). A total of 19 stents were placed successfully. The dysphagia grade prior to and after oesophageal stent placement was assessed and the complications documented. Of the 17 patients, 16 reported an improvement in dysphagia. The mean dysphagia score improved from 3.1 prior to treatment to 1.3 after treatment. In 1 patient the stent slipped during placement and another stent was placed satisfactorily. Early complications (within 48 h) in the form of mild to moderate retrosternal chest pain occurred in 5 patients. This was treated symptomatically. Late complications (after 48 h) in the form of bolus impaction occurred in 2 patients. This was successfully treated with oesophagoscopy and removal of bolus. In 2 patients the stent was overgrown by tumour and in one of these an additional stent was placed. In 1 patient incomplete closure of a tracheo-oesophageal fistula was observed. There was no procedure- or stent-related mortality. The mean survival time of this group was 2.1 months. Self-expanding metallic stents can be safely and effectively used in the palliation of dysphagia due to external mediastinal malignancies. (orig.)

Self-expanding oesophageal metal stents for the palliation of dysphagia due to extrinsic compression

International Nuclear Information System (INIS)

Gupta, N.K.; Boylan, C.E.; Razzaq, R.; England, R.E.; Mirra, L.; Martin, D.F.

1999-01-01

The role of self-expanding metallic stents is well established in the palliation of oesophageal stenosis and dysphagia due to primary oesophageal malignancy. However, their role in palliation of dysphagia due to external compressive mediastinal malignancies is not well established. The purpose of this study was to assess the efficacy of self-expanding metallic stents in the palliation of dysphagia due to extrinsic oesophageal compression by mediastinal malignancy. Between January 1995 and January 1998, 21 patients with oesophageal compression due to malignant mediastinal tumours underwent oesophageal stent placement for palliation of dysphagia. Complete data were available in 17 patients (10 men and 7 women). The mean age was 63.5 years (range 46-89 years). A total of 19 stents were placed successfully. The dysphagia grade prior to and after oesophageal stent placement was assessed and the complications documented. Of the 17 patients, 16 reported an improvement in dysphagia. The mean dysphagia score improved from 3.1 prior to treatment to 1.3 after treatment. In 1 patient the stent slipped during placement and another stent was placed satisfactorily. Early complications (within 48 h) in the form of mild to moderate retrosternal chest pain occurred in 5 patients. This was treated symptomatically. Late complications (after 48 h) in the form of bolus impaction occurred in 2 patients. This was successfully treated with oesophagoscopy and removal of bolus. In 2 patients the stent was overgrown by tumour and in one of these an additional stent was placed. In 1 patient incomplete closure of a tracheo-oesophageal fistula was observed. There was no procedure- or stent-related mortality. The mean survival time of this group was 2.1 months. Self-expanding metallic stents can be safely and effectively used in the palliation of dysphagia due to external mediastinal malignancies. (orig.)

Stability of River Bifurcations from Bedload to Suspended Load Dominated Conditions

Science.gov (United States)

de Haas, T.; Kleinhans, M. G.

2010-12-01

Bifurcations (also called diffluences) are as common as confluences in braided and anabranched rivers, and more common than confluences on alluvial fans and deltas where the network is essentially distributary. River bifurcations control the partitioning of both water and sediment through these systems with consequences for immediate river and coastal management and long-term evolution. Their stability is poorly understood and seems to differ between braided rivers, meandering river plains and deltas. In particular, it is the question to what extent the division of flow is asymmetrical in stable condition, where highly asymmetrical refers to channel closure and avulsion. Recent work showed that bifurcations in gravel bed braided rivers become more symmetrical with increasing sediment mobility, whereas bifurcations in a lowland sand delta become more asymmetrical with increasing sediment mobility. This difference is not understood and our objective is to resolve this issue. We use a one-dimensional network model with Y-shaped bifurcations to explore the parameter space from low to high sediment mobility. The model solves gradually varied flow, bedload transport and morphological change in a straightforward manner. Sediment is divided at the bifurcation including the transverse slope effect and the spiral flow effect caused by bends at the bifurcation. Width is evolved whilst conserving mass of eroded or built banks with the bed balance. The bifurcations are perturbed from perfect symmetry either by a subtle gradient advantage for one branch or a gentle bend at the bifurcation. Sediment transport was calculated with and without a critical threshold for sediment motion. Sediment mobility, determined in the upstream channel, was varied in three different ways to isolate the causal factor: by increasing discharge, increasing channel gradient and decreasing particle size. In reality the sediment mobility is mostly determined by particle size: gravel bed rivers are near

Evaluation of anti-migration properties of biliary covered self-expandable metal stents.

Science.gov (United States)

Minaga, Kosuke; Kitano, Masayuki; Imai, Hajime; Harwani, Yogesh; Yamao, Kentaro; Kamata, Ken; Miyata, Takeshi; Omoto, Shunsuke; Kadosaka, Kumpei; Sakurai, Toshiharu; Nishida, Naoshi; Kudo, Masatoshi

2016-08-14

To assess anti-migration potential of six biliary covered self-expandable metal stents (C-SEMSs) by using a newly designed phantom model. In the phantom model, the stent was placed in differently sized holes in a silicone wall and retracted with a retraction robot. Resistance force to migration (RFM) was measured by a force gauge on the stent end. Radial force (RF) was measured with a RF measurement machine. Measured flare structure variables were the outer diameter, height, and taper angle of the flare (ODF, HF, and TAF, respectively). Correlations between RFM and RF or flare variables were analyzed using a linear correlated model. Out of the six stents, five stents were braided, the other was laser-cut. The RF and RFM of each stent were expressed as the average of five replicate measurements. For all six stents, RFM and RF decreased as the hole diameter increased. For all six stents, RFM and RF correlated strongly when the stent had not fully expanded. This correlation was not observed in the five braided stents excluding the laser cut stent. For all six stents, there was a strong correlation between RFM and TAF when the stent fully expanded. For the five braided stents, RFM after full stent expansion correlated strongly with all three stent flare structure variables (ODF, HF, and TAF). The laser-cut C-SEMS had higher RFMs than the braided C-SEMSs regardless of expansion state. RF was an important anti-migration property when the C-SEMS did not fully expand. Once fully expanded, stent flare structure variables plays an important role in anti-migration.

Aortic regurgitation after valve-sparing aortic root replacement: modes of failure.

Science.gov (United States)

Oka, Takanori; Okita, Yutaka; Matsumori, Masamichi; Okada, Kenji; Minami, Hitoshi; Munakata, Hiroshi; Inoue, Takeshi; Tanaka, Akiko; Sakamoto, Toshihito; Omura, Atsushi; Nomura, Takuo

2011-11-01

Despite the positive clinical results of valve-sparing aortic root replacement, little is known about the causes of reoperations and the modes of failure. From October 1999 to June 2010, 101 patients underwent valve-sparing aortic root replacement using the David reimplantation technique. The definition of aortic root repair failure included the following: (1) intraoperative conversion to the Bentall procedure; (2) reoperation performed because of aortic regurgitation; and (3) aortic regurgitation equal to or greater than a moderate degree at the follow-up. Sixteen patients were considered to have repair failure. Three patients required intraoperative conversion to valve replacement, 3 required reoperation within 3 months, and another 8 required reoperation during postoperative follow-up. At initial surgery 5 patients had moderate to severe aortic regurgitation, 6 patients had acute aortic dissections, 3 had Marfan syndrome, 2 had status post Ross operations, 3 had bicuspid aortic valves, and 1 had aortitis. Five patients had undergone cusp repair, including Arantius plication in 3 and plication at the commissure in 2. The causes of early failure in 6 patients included cusp perforation (3), cusp prolapse (3), and severe hemolysis (1). The causes of late failure in 10 patients included cusp prolapse (4), commissure dehiscence (3), torn cusp (2), and cusp retraction (1). Patients had valve replacements at a mean of 23 ± 20.9 months after reimplantation and survived. Causes of early failure after valve-sparing root replacement included technical failure, cusp lesions, and steep learning curve. Late failure was caused by aortic root wall degeneration due to gelatin-resorcin-formalin glue, cusp degeneration, or progression of cusp prolapse. Copyright © 2011 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.

Aortic intramural hematoma : assessment of clinical and radiological features in comparison to acute aortic dissection

International Nuclear Information System (INIS)

Yoon, Kwon Ha; Hwang, Jae Cheol; Lee, Jin Seong; Kang, Duk Hyun; Song, Jae Kwan; Song, Koun Sik; Lim, Tae Hwan

1996-01-01

To compare the clinical and radiological features of aortic intramural hematoma(IMH) to those of acute aortic dissection(AD). We analyzed the clinical and radiological features of 12 patients with aortic IMH and 43 patients with acute AD. In aortic IMH, the diagnoses were made by means of both CT and transesophageal echocardiography(TEE) and included two surgically proven cases. In acute AD, the diagnoses were made by means of CT and TEE and included 21 surgically proven cases. We compared patients ages, etiologies, the extent of the disease, the presence or absence of aortic branch involvement, complications, and outcomes. Aortic IMH tended to develop in older patients (67.8±7.9 vs. 50.4±13.4, P .05). In aortic IMH, there was no involvement of aortic branches, whereas in acute AD, 14(33%) patients showed involvement of one or more aortic branches. Complications of aortic IMH included pericardial effusion (n=2) and pleural effusion (n=4);in acute AD, pericardial effusion (n=7), pleural effusion (n=4), aortic insufficiency (n=8), cerebral infarction (n=3), renal infarction (n=4) and spinal infarction (n=1) were seen. There was one (8%) death due to aortic IMH and ten (23%) deaths due to acute AD (p<.01). Aortic IMH is characterized by its occurrence in older patients with hypertension, a less frequent incidence of complications, and a more favorable outcome than acute AD

Assessment of structural valve deterioration of transcatheter aortic bioprosthetic balloon-expandable valves using the new European consensus definition.

Science.gov (United States)

Eltchaninoff, Hélène; Durand, Eric; Avinée, Guillaume; Tron, Christophe; Litzler, Pierre-Yves; Bauer, Fabrice; Dacher, Jean-Nicolas; Werhlin, Camille; Bouhzam, Najime; Bettinger, Nicolas; Candolfi, Pascal; Cribier, Alain

2018-03-30

Durability of transcatheter aortic bioprosthetic valves remains a major issue. Standardised definitions of deterioration and failure of bioprosthetic valves have recently been proposed. The aim of this study was to assess structural transcatheter valve deterioration (SVD) and bioprosthetic valve failure (BVF) using these new definitions. All TAVI patients implanted up to September 2012 with a minimal theoretical five-year follow-up were included. Systematic clinical and echocardiographic follow-up was performed annually. New standardised definitions were used to assess durability of transcatheter aortic bioprosthetic valves. From 2002 to 2012, 378 patients were included. Mean age and logistic EuroSCORE were 83.3±6.8 years and 22.8±13.1%. Thirty-day mortality was 13.2%. Nine patients had SVD including two severe forms and two patients had definite late BVF. The incidence of SVD and BVF at eight years was 3.2% (95% CI: 1.45-6.11) and 0.58% (95% CI: 0.15-2.75), respectively. Even though limited by the poor survival of the very high-risk/compassionate early population, our data do not demonstrate any alarm concerning transcatheter aortic valve durability. Careful prospective assessment in younger and lower-risk patients and comparison with surgical bioprosthetic valves are required for further assessment of the long-term durability of transcatheter valves.

Transcatheter aortic valve replacement

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... gov/ency/article/007684.htm Transcatheter aortic valve replacement To use the sharing features on this page, please enable JavaScript. Transcatheter aortic valve replacement (TAVR) is surgery to replace the aortic valve. ...

Left Ventricular Assist Device Implantation with Concomitant Aortic Valve and Ascending Aortic Replacement.

Science.gov (United States)

Huenges, Katharina; Panholzer, Bernd; Cremer, Jochen; Haneya, Assad

2018-01-01

Left ventricular assist device (LVAD) is nowadays a routine therapy for patients with advanced heart failure. We present the case of a 74-year-old male patient who was admitted to our center with terminal heart failure in dilated cardiomyopathy and ascending aortic aneurysm with aortic valve regurgitation. The LVAD implantation with simultaneous aortic valve and supracoronary ascending aortic replacement was successfully performed.

Bifurcation of Jovian magnetotail current sheet

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P. L. Israelevich

2006-07-01

Full Text Available Multiple crossings of the magnetotail current sheet by a single spacecraft give the possibility to distinguish between two types of electric current density distribution: single-peaked (Harris type current layer and double-peaked (bifurcated current sheet. Magnetic field measurements in the Jovian magnetic tail by Voyager-2 reveal bifurcation of the tail current sheet. The electric current density possesses a minimum at the point of the B_x-component reversal and two maxima at the distance where the magnetic field strength reaches 50% of its value in the tail lobe.

Riddling bifurcation and interstellar journeys

International Nuclear Information System (INIS)

Kapitaniak, Tomasz

2005-01-01

We show that riddling bifurcation which is characteristic for low-dimensional attractors embedded in higher-dimensional phase space can give physical mechanism explaining interstellar journeys described in science-fiction literature

Arctic melt ponds and bifurcations in the climate system

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Sudakov, I.; Vakulenko, S. A.; Golden, K. M.

2015-05-01

Understanding how sea ice melts is critical to climate projections. In the Arctic, melt ponds that develop on the surface of sea ice floes during the late spring and summer largely determine their albedo - a key parameter in climate modeling. Here we explore the possibility of a conceptual sea ice climate model passing through a bifurcation point - an irreversible critical threshold as the system warms, by incorporating geometric information about melt pond evolution. This study is based on a bifurcation analysis of the energy balance climate model with ice-albedo feedback as the key mechanism driving the system to bifurcation points.

Stochastic Bifurcation Analysis of an Elastically Mounted Flapping Airfoil

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Bose Chandan

2018-01-01

Full Text Available The present paper investigates the effects of noisy flow fluctuations on the fluid-structure interaction (FSI behaviour of a span-wise flexible wing modelled as a two degree-of-freedom elastically mounted flapping airfoil. In the sterile flow conditions, the system undergoes a Hopf bifurcation as the free-stream velocity exceeds a critical limit resulting in a stable limit-cycle oscillation (LCO from a fixed point response. On the other hand, the qualitative dynamics changes from a stochastic fixed point to a random LCO through an intermittent state in the presence of irregular flow fluctuations. The probability density function depicts the most probable system state in the phase space. A phenomenological bifurcation (P-bifurcation analysis based on the transition in the topology associated with the structure of the joint probability density function (pdf of the response variables has been carried out. The joint pdf corresponding to the stochastic fixed point possesses a Dirac delta function like structure with a sharp single peak around zero. As the mean flow speed crosses the critical value, the joint pdf bifurcates to a crater-like structure indicating the occurrence of a P-bifurcation. The intermittent state is characterized by the co-existence of the unimodal as well as the crater like structure.

Endovascular repair of arterial iliac vessel wall lesions with a self-expandable nitinol stent graft system.

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Birger Mensel

Full Text Available To assess the therapeutic outcome after endovascular repair of iliac arterial lesions (IALs using a self-expandable Nitinol stent graft system.Between July 2006 and March 2013, 16 patients (13 males, mean age: 68 years with a self-expandable Nitinol stent graft. A total of 19 lesions were treated: nine true aneurysms, two anastomotic aneurysms, two dissections, one arteriovenous fistula, two type 1B endoleaks after endovascular aneurysm repair, one pseudoaneurysm, and two perforations after angioplasty. Pre-, intra-, and postinterventional imaging studies and the medical records were analyzed for technical and clinical success and postinterventional complications.The primary technical and clinical success rate was 81.3% (13/16 patients and 75.0% (12/16, respectively. Two patients had technical failure due to persistent type 1A endoleak and another patient due to acute stent graft thrombosis. One patient showed severe stent graft kinking on the first postinterventional day. In two patients, a second intervention was performed. The secondary technical and clinical success rate was 87.5% (14/16 and 93.8% (15/16. The minor complication rate was 6.3% (patient with painful hematoma at the access site. The major complication rate was 6.3% (patient with ipsilateral deep vein thrombosis. During median follow-up of 22.4 months, an infection of the aneurysm sac in one patient and a stent graft thrombosis in another patient were observed.Endovascular repair of various IALs with a self-expandable Nitinol stent graft is safe and effective.

Infected aortic aneurysm and inflammatory aortic aneurysm. In search of an optimal differential diagnosis

International Nuclear Information System (INIS)

Ishizaka, Nobukazu; Sohmiya, Koichi; Miyamura, Masatoshi; Umeda, Tatsuya; Tsuji, Motomu; Katsumata, Takahiro; Miyata, Tetsuro

2012-01-01

Infected aortic aneurysm and inflammatory aortic aneurysm each account for a minor fraction of the total incidence of aortic aneurysm and are associated with periaortic inflammation. Despite the similarity, infected aortic aneurysm generally shows a more rapid change in clinical condition, leading to a fatal outcome; in addition, delayed diagnosis and misuse of corticosteroid or immunosuppressing drugs may lead to uncontrolled growth of microorganisms. Therefore, it is mandatory that detection of aortic aneurysm is followed by accurate differential diagnosis. In general, infected aortic aneurysm appears usually as a saccular form aneurysm with nodularity, irregular configuration; however, the differential diagnosis may not be easy sometimes for the following reasons: symptoms, such as abdominal and/or back pain and fever, and blood test abnormalities, such as elevated C-reactive protein and enhanced erythrocyte sedimentation rate, are common in infected aortic aneurysm, but they are not found infrequently in inflammatory aortic aneurysm; some inflammatory aortic aneurysms are immunoglobulin (Ig) G4-related, but not all of them; the prevalence of IgG4 positivity in infected aortic aneurysm has not been well investigated; enhanced uptake of 18F-fluorodeoxyglucose (FDG) by 18F-FDG-positron emission tomography may not distinguish between inflammation mediated by autoimmunity and that mediated by microorganism infection. Here we discuss the characteristics of these two forms of aortic aneurysm and the points of which we have to be aware before reaching a final diagnosis. (author)

Bifurcation diagram features of a dc-dc converter under current-mode control

International Nuclear Information System (INIS)

Ruzbehani, Mohsen; Zhou Luowei; Wang Mingyu

2006-01-01

A common tool for analysis of the systems dynamics when the system has chaotic behaviour is the bifurcation diagram. In this paper, the bifurcation diagram of an ideal model of a dc-dc converter under current-mode control is analysed. Algebraic relations that give the critical points locations and describe the pattern of the bifurcation diagram are derived. It is shown that these simple algebraic and geometrical relations are responsible for the complex pattern of the bifurcation diagrams in such circuits. More explanation about the previously observed properties and introduction of some new ones are exposited. In addition, a new three-dimensional bifurcation diagram that can give better imagination of the parameters role is introduced

Frequency locking, quasiperiodicity, subharmonic bifurcations and chaos in high frequency modulated stripe geometry DH semiconductor lasers

International Nuclear Information System (INIS)

Zhao Yiguang

1991-01-01

The method of obtaining self-consistent solutions of the field equation and the rate equations of photon density and carrier concentration has been used to study frequecny locking, quasiperiodicity, subharmonic bifurcations and chaos in high frequency modulated stripe geometry DH semiconductor lasers. The results show that the chaotic behavior arises in self-pulsing stripe geometry semiconductor lasers. The route to chaos is not period-double, but quasiperiodicity to chaos. All of the results agree with the experiments. Some obscure points in previous theory about chaos have been cleared up

Modified jailed balloon technique for bifurcation lesions.

Science.gov (United States)

Saito, Shigeru; Shishido, Koki; Moriyama, Noriaki; Ochiai, Tomoki; Mizuno, Shingo; Yamanaka, Futoshi; Sugitatsu, Kazuya; Tobita, Kazuki; Matsumi, Junya; Tanaka, Yutaka; Murakami, Masato

2017-12-04

We propose a new systematic approach in bifurcation lesions, modified jailed balloon technique (M-JBT), and report the first clinical experience. Side branch occlusion brings with a serious complication and occurs in more than 7.0% of cases during bifurcation stenting. A jailed balloon (JB) is introduced into the side branch (SB), while a stent is placed in the main branch (MB) as crossing SB. The size of the JB is half of the MB stent size. While the proximal end of JB attaching to MB stent, both stent and JB are simultaneously inflated with same pressure. JB is removed and then guidewires are recrossed. Kissing balloon dilatation (KBD) and/or T and protrusion (TAP) stenting are applied as needed. Between February 2015 and February 2016, 233 patients (254 bifurcation lesions including 54 left main trunk disease) underwent percutaneous coronary intervention (PCI) using this technique. Procedure success was achieved in all cases. KBD was performed for 183 lesions and TAP stenting was employed for 31 lesions. Occlusion of SV was not observed in any of the patients. Bench test confirmed less deformity of MB stent in M-JBT compared with conventional-JBT. This is the first report for clinical experiences by using modified jailed balloon technique. This novel M-JBT is safe and effective in the preservation of SB patency during bifurcation stenting. © 2017 Wiley Periodicals, Inc.

A bench top experimental model of bubble transport in multiple arteriole bifurcations

International Nuclear Information System (INIS)

Eshpuniyani, Brijesh; Fowlkes, J. Brian; Bull, Joseph L.

2005-01-01

Motivated by a novel gas embolotherapy technique, a bench top vascular bifurcation model is used to investigate the splitting of long bubbles in a series of liquid-filled bifurcations. The developmental gas embolotherapy technique aims to treat cancer by infarcting tumors with gas emboli that are formed by selective acoustic vaporization of ∼6 μm, intravascular, perfluorcarbon droplets. The resulting gas bubbles are large enough to extend through several vessel bifurcations. The current bench top experiments examine the effects of gravity and flow on bubble transport through multiple bifurcations. The effect of gravity is varied by changing the roll angle of the bifurcating network about its parent tube. Splitting at each bifurcation is nearly even when the roll angle is zero. It is demonstrated that bubbles can either stick at one of the second bifurcations or in the second generation daughter tubes, even though the flow rate in the parent tube is constant. The findings of this work indicate that both gravity and flow are important in determining the bubble transport, and suggest that a treatment strategy that includes multiple doses may be effective in delivering emboli to vessels not occluded by the initial dose

Aortic root surgery in Marfan syndrome: Comparison of aortic valve-sparing reimplantation versus composite grafting.

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Karck, Matthias; Kallenbach, Klaus; Hagl, Christian; Rhein, Christine; Leyh, Rainer; Haverich, Axel

2004-02-01

The objective of this study was to compare the results of aortic valve-sparing reimplantation and aortic root replacement with mechanical valve conduits in patients with Marfan syndrome undergoing operation for aortic root aneurysms. Patients and methods Between March 1979 and April 2002, 119 patients with clinical evidence of Marfan syndrome underwent composite graft replacement with mechanical valve conduits (n = 74) or aortic valve-sparing reimplantation according to David (n = 45). The underlying causes were aortic dissection type A (43 patients) and aneurysms (76 patients). Patients undergoing aortic valve reimplantation were younger compared with patients undergoing composite grafting (28 vs 35 years, P =.002) and had longer intraoperative aortic crossclamp times (125 vs 78 minutes, P valve reimplantation (P =.15). Mean follow-up was 30 months for patients undergoing aortic valve reimplantation and 114 months for patients undergoing composite grafting. Freedom from reoperation and death after 5 years postoperatively was 92% and 89% in patients undergoing composite grafting and 84% and 96% in patients undergoing aortic valve reimplantation (P =.31; P =.54), respectively. Thromboembolic complications or late postoperative bleeding occurred in 17 patients undergoing composite grafting, and an early postoperative event occurred in 1 patient undergoing aortic valve reimplantation. The results of aortic valve reimplantation and composite grafting of the aortic valve and ascending aorta with mechanical valve conduits are similar with regard to early and mid-term postoperative mortality and to the incidence of late reoperations in patients with Marfan syndrome. The low risk of thromboembolic or bleeding complications favors aortic valve reimplantation in these patients.

Novel biliary self-expanding metal stents: indications and applications.

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Blero, Daniel; Huberty, Vincent; Devière, Jacques

2015-03-01

Endoscopic insertion of a self-expanding metal stent (SEMS) through a malignant common bile duct stricture is the first line of palliation for malignant jaundice. Patency of these stents remains a major concern. SEMS dysfunction can result from tumor ingrowth, overgrowth and/or clogging. Initial SEMS modifications involved covering the central part of the stent in order to reduce ingrowth and ultimately increase patency. Fully covered stents became available shortly after reports of their use in human patients. The potential removability and radial strength of SEMS have led to evaluation of their use in new indications including benign biliary strictures, post sphincterotomy bleeding and perforation. Other aspects of development include the addition of features such as anti-reflux valves, drug elution and spontaneous biodegradability. These aspects and their clinical implications are reviewed and discussed.

A case of acute ischemic colitis after endovascular abdominal aortic aneurysm repair

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Grigorios Voulalas

2016-01-01

Full Text Available Colonic ischemia is a recognized complication of either open or endovascular abdominal aortic aneurysm repair. The clinical difficulty in establishing the diagnosis, the severity of this complication and the patient's poor physiological status may lead to a fatal outcome. We presented a case of ischemic colitis in a patient with patent hypogastric arteries that occurred after an endovascular abdominal aortic aneurysm repair as well as a review of the available literature. The patient's preoperative, intraoperative and postoperative data were recorded. A thorough search through the Google data and Medline to review similar cases or any analyses that referred to ischemic colitis after endovascular abdominal aneurysm repair was conducted. A 76-year-old male was admitted to our department for an elective endovascular repair of an 8 cm in diameter abdominal aortic aneurysm. A Zenith bifurcation graft was implanted. The whole procedure was uneventful and the final angiogram showed an accurate deployment of the endograft without endoleaks and patency of both hypogastric arteries. During the 1st postoperative day, the patient developed symptoms of acute abdomen in combination with metabolic acidosis and oliguria. He underwent an exploratory laparotomy, which revealed necrosis of the sigmoid. A Hartmann's procedure was performed; the patient was transferred to the intensive care unit where he deceased after 24 h. Postoperative ischemic colitis has been described after open abdominal aneurysm repair. The description of this complication has been reported since the early phase of endovascular abdominal aneurysm repair development with a current incidence of 1.5%–3.0%. Possible mechanisms that may contribute to ischemic colitis in spite of the presence of patent hypogastric arteries include atheroembolization, shock, vasopressive drugs and inferior mesenteric artery occlusion.

Experimental Investigation of Bifurcations in a Thermoacoustic Engine

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Vishnu R. Unni

2015-06-01

Full Text Available In this study, variation in the characteristics of the pressure oscillations in a thermoacoustic engine is explored as the input heat flux is varied. A bifurcation diagram is plotted to study the variation in the qualitative behavior of the acoustic oscillations as the input heat flux changes. At a critical input heat flux (60 Watt, the engine begins to produce acoustic oscillations in its fundamental longitudinal mode. As the input heat flux is increased, incommensurate frequencies appear in the power spectrum. The simultaneous presence of incommensurate frequencies results in quasiperiodic oscillations. On further increase of heat flux, the fundamental mode disappears and second mode oscillations are observed. These bifurcations in the characteristics of the pressure oscillations are the result of nonlinear interaction between multiple modes present in the thermoacoustic engine. Hysteresis in the bifurcation diagram suggests that the bifurcation is subcritical. Further, the qualitative analysis of different dynamic regimes is performed using nonlinear time series analysis. The physical reason for the observed nonlinear behavior is discussed. Suggestions to avert the variations in qualitative behavior of the pressure oscillations in thermoacoustic engines are also provided.

Anatomy of the Portal Vein Bifurcation: Implication for Transjugular Intrahepatic Portal Systemic Shunts

International Nuclear Information System (INIS)

Kwok, Philip Chong-hei; Ng, Wai Fu; Lam, Christine Suk-yee; Tsui, Polly Po; Faruqi, Asma

2003-01-01

Purpose: The relationship of the portalvein bifurcation to the liver capsule in Asians, which is an important landmark for transjugular intrahepatic portosystemic shunt, has not previously been described. Methods: The anatomy of the portal vein bifurcation was studied in 70 adult Chinese cadavers; it was characterized as intrahepatic or extrahepatic. The length of the exposed portion of the right and left portal veins was measured when the bifurcation was extrahepatic. Results: The portal vein bifurcation was intrahepatic in 37 cadavers (53%) and extrahepatic in 33 cadavers (47%). The mean length of the right and left extrahepatic portal veins was 0.96 cm and 0.85 cm respectively.Both were less than or equal to 2 cm in 94% of the cadavers with extrahepatic bifurcation. There was no correlation between the presence of cirrhosis and the location of the portal vein bifurcation(p 1.0). There was no statistically significant difference in liver mass in cadavers with either extrahepatic or intrahepatic bifurcation (p =0.40). Conclusions: These findings suggest that fortransjugular intrahepatic portosystemic shunt placement, a portal vein puncture 2 cm from the bifurcation will be safe in most cases

Bifurcation Analysis and Spatiotemporal Patterns in Unidirectionally Delay-Coupled Vibratory Gyroscopes

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Li, Li; Xu, Jian

Time delay is inevitable in unidirectionally coupled drive-free vibratory gyroscope system. The effect of time delay on the gyroscope system is studied in this paper. To this end, amplitude death and Hopf bifurcation induced by small time delay are first investigated by analyzing the related characteristic equation. Then, the direction of Hopf bifurcations and stability of Hopf-bifurcating periodic oscillations are determined by calculating the normal form on the center manifold. Next, spatiotemporal patterns of these Hopf-bifurcating periodic oscillations are analyzed by using the symmetric bifurcation theory of delay differential equations. Finally, it is found that numerical simulations agree with the associated analytic results. These phenomena could be induced although time delay is very small. Therefore, it is shown that time delay is an important factor which influences the sensitivity and accuracy of the gyroscope system and cannot be neglected during the design and manufacture.

Physical property and MR imaging of self-expandable metallic stents

Energy Technology Data Exchange (ETDEWEB)

Roh, Hong Gee; Kang, Sung Gwon; Cho, Young Kook; Kim, Hyung Jin; Lim, Myung Kwan; Cho, Soon Gu; Yoh, Kyu Tong; Suh, Chang Hae [Inha Univ., College of Medicine, Seoul (Korea, Republic of)

1998-09-01

In order to furnish basic information prior to their use, the physical properties of various self-expandable metallic stents and their MR characteristics were evaluated. Four commercially available self-expandable metallic stents-Gianturco-the Rosch, Hanaro, Memotherm, and Wallstent-were used in this study. For evaluation of the physical properties of each, hoop strengths and changes in radii according to the degrees of longitudinal flexion were compared. Stent characteristics seen on MR images were evaluated by measuring magnetic torque and by comparing images obtained in the vascular phantom using SE T1TI, FSE T2WI, and FMPSPGR sequences. These images were analyzed with special emphasis on artifact size and the apparant shepe of the stent. Hoop strength was greatest in the Gianturco-Rosch stent, followed by the Memotherm, Hanaro, and Wallstent. When flexed in the longitudinal axis, the radius of the Hanaro and Memotherm stent decreased slightly as a larger flexion angle was applied. When this was 90 deg, however, the connection of the Gianturco-Rosch stent collapsed. In contrast, the radius of the Wallstent became larger as a larger flexion angle was applied. At the portal of the MR imaging unit, neither the Memotherm nor Wallstent showed deflection; except for a thin hyperintense rim at both ends, their images were excellent, and the lumina of these stents were also clearly seen. In contrast, the Gianturco-Rosch and Hanaro stent demonstrated large deflexion and showed a severe black-hole artifact. As a result, visualization of the stents themselves and their lumina was impossible. The Gianturco-Rosch stent showed greatrer hoop strength than the others. The Wallstent showed good longitudinal flexibility and was thought to be effective in tortuous vessels. For follow-up after placement, especially when the nonferromagnetic Memotherm and Wallstent are used, MR imaging appears to be safe and useful.=20.

Management of post-gastrectomy anastomosis site obstruction with a self-expandable metallic stent.

Science.gov (United States)

Cha, Ra Ri; Lee, Sang Soo; Kim, Hyunjin; Kim, Hong Jun; Kim, Tae-Hyo; Jung, Woon Tae; Lee, Ok Jae; Bae, Kyung Soo; Jeong, Sang-Ho; Ha, Chang Yoon

2015-04-28

Post-gastrectomy anastomosis site obstruction is a relatively rare complication after a subtotal gastrectomy. We present a case of a 75-year-old man who underwent a truncal vagotomy, omental patch, gastrojejunostomy, and Braun anastomosis for duodenal ulcer perforation and a gastric outlet obstruction. Following the 10(th) postoperative day, the patient complained of abdominal discomfort and vomiting. We diagnosed post-gastrectomy anastomosis site obstruction by an upper gastrointestinal series and an upper endoscopic examination. We inserted a self-expandable metallic stent (SEMS) at the anastomosis site. The stent was fully expanded after deployment. On the day following the stent insertion, the patient began to eat, and his abdominal discomfort was resolved. This paper describes the successful management of post-gastrectomy anastomosis site obstruction with temporary placement of a SEMS.

Lightweight self-compacting concrete with light expanded clay aggregate (LECA

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Heiza Khaled

2018-01-01

Full Text Available Lightweight concretes have been successfully applied in building constructions for many years due to their favorable material properties, particularly their low specific weight in connection with a high strength, a high capability of thermal insulation and a high durability. The development leading to lightweight self-compacting concrete (LWSCC represents an important advanced step within the recent years. This concrete combines the favorable properties of a lightweight concrete with those of a self-compacting concrete. Research work is aimed on development of (LWSCC with the use of light aggregates “Light expanded clay aggregate (LECA”. In this research, first by specific gravity factor method, twenty different mix designs of (LWSCC were cast and tested to find out the values of slump flow, J-ring , V-funnel and 28 day compressive strength. Based on the results obtained, the best mix design was selected for further investigation. This paper also focuses on studying the effect of changing the reinforcement ratio on reinforced two way slabs when the dimensions were kept constant.

Aortic valve-sparing operations in aortic root aneurysms: remodeling or reimplantation?

Science.gov (United States)

Rahnavardi, Mohammad; Yan, Tristan D; Bannon, Paul G; Wilson, Michael K

2011-08-01

A best evidence topic was written according to a structured protocol. The question addressed was whether the reimplantation (David) technique or the remodeling (Yacoub) technique provides the optimum event free survival in patients with an aortic root aneurysm suitable for an aortic valve-sparing operation. In total, 392 papers were found using the reported search criteria, of which 14 papers provided the best evidence to answer the clinical question. A total of 1338 patients (Yacoub technique in 606 and David technique in 732) from 13 centres were included. In most series, cardiopulmonary bypass time and aortic cross-clamp time were longer for the David technique compared to the Yacoub technique. Early mortality was comparable between the two techniques (0-6.9% for the Yacoub technique and 0-6% for the David technique). There is a tendency for a higher freedom from significant long-term aortic insufficiency in the David group than the Yacoub group, which does not necessarily result in a higher reoperation rate in the Yacoub group. In the largest series reported, freedom from a moderate-to-severe aortic insufficiency at 12 years was 82.6 ± 6.2% in the Yacoub and 91.0 ± 3.8% in the David group (P=0.035). Freedom from reoperation at the same time point was 90.4 ± 4.7% in the Yacoub group and 97.4 ± 2.2% in the David group (P=0.09). In another series, freedom from reoperation at a follow-up time of about four years was 89 ± 4% in the Yacoub group and 98 ± 2% in the David group. Although some authors merely preferred the Yacoub technique for a bicuspid aortic valve, the accumulated evidence in the current review indicates comparable results for both techniques in a bicuspid aortic valve. Current evidence is in favour of the David rather than the Yacoub technique in pathologies such as Marfan syndrome, acute type A aortic dissection, and excessive annular dilatation that may impair aortic root integrity. Careful selection of patients for each technique and

Incidence and progression of mild aortic regurgitation after Tirone David reimplantation valve-sparing aortic root replacement.

Science.gov (United States)

Stephens, Elizabeth H; Liang, David H; Kvitting, John-Peder Escobar; Kari, Fabian A; Fischbein, Michael P; Mitchell, R Scott; Miller, D Craig

2014-01-01

The study objective was to determine whether recurrent or residual mild aortic regurgitation, which occurs after valve-sparing aortic root replacement, progresses over time. Between 2003 and 2008, 154 patients underwent Tirone David-V valve-sparing aortic root replacement; 96 patients (62%) had both 1-year (median, 12 ± 4 months) and mid-term (62 ± 22 months) transthoracic echocardiograms available for analysis. Age of patients averaged 38 ± 13 years, 71% were male, 31% had a bicuspid aortic valve, 41% had Marfan syndrome, and 51% underwent aortic valve repair, predominantly cusp free margin shortening. Forty-one patients (43%) had mild aortic regurgitation on 1-year echocardiogram. In 85% of patients (n = 35), mild aortic regurgitation remained stable on the most recent echocardiogram (median, 57 ± 20 months); progression to moderate aortic regurgitation occurred in 5 patients (12%) at a median of 28 ± 18 months and remained stable thereafter; severe aortic regurgitation developed in 1 patient, eventually requiring reoperation. Five patients (5%) had moderate aortic regurgitation at 1 year, which did not progress subsequently. Two patients (2%) had more than moderate aortic regurgitation at 1 year, and both ultimately required reoperation. Although mild aortic regurgitation occurs frequently after valve-sparing aortic root replacement, it is unlikely to progress over the next 5 years and should not be interpreted as failure of the valve-preservation concept. Further, we suggest that mild aortic regurgitation should not be considered nonstructural valve dysfunction, as the 2008 valve reporting guidelines would indicate. We need 10- to 15-year follow-up to learn the long-term clinical consequences of mild aortic regurgitation early after valve-sparing aortic root replacement. Copyright © 2014 The American Association for Thoracic Surgery. Published by Mosby, Inc. All rights reserved.

Do ants need to estimate the geometrical properties of trail bifurcations to find an efficient route? A swarm robotics test bed.

Directory of Open Access Journals (Sweden)

Simon Garnier

Full Text Available Interactions between individuals and the structure of their environment play a crucial role in shaping self-organized collective behaviors. Recent studies have shown that ants crossing asymmetrical bifurcations in a network of galleries tend to follow the branch that deviates the least from their incoming direction. At the collective level, the combination of this tendency and the pheromone-based recruitment results in a greater likelihood of selecting the shortest path between the colony's nest and a food source in a network containing asymmetrical bifurcations. It was not clear however what the origin of this behavioral bias is. Here we propose that it results from a simple interaction between the behavior of the ants and the geometry of the network, and that it does not require the ability to measure the angle of the bifurcation. We tested this hypothesis using groups of ant-like robots whose perceptual and cognitive abilities can be fully specified. We programmed them only to lay down and follow light trails, avoid obstacles and move according to a correlated random walk, but not to use more sophisticated orientation methods. We recorded the behavior of the robots in networks of galleries presenting either only symmetrical bifurcations or a combination of symmetrical and asymmetrical bifurcations. Individual robots displayed the same pattern of branch choice as individual ants when crossing a bifurcation, suggesting that ants do not actually measure the geometry of the bifurcations when travelling along a pheromone trail. Finally at the collective level, the group of robots was more likely to select one of the possible shorter paths between two designated areas when moving in an asymmetrical network, as observed in ants. This study reveals the importance of the shape of trail networks for foraging in ants and emphasizes the underestimated role of the geometrical properties of transportation networks in general.

Analysis of the flow at a T-bifurcation for a ternary unit

International Nuclear Information System (INIS)

Campero, P; Beck, J; Jung, A

2014-01-01

The motivation of this research is to understand the flow behavior through a 90° T- type bifurcation, which connects a Francis turbine and the storage pump of a ternary unit, under different operating conditions (namely turbine, pump and hydraulic short-circuit operation). As a first step a CFD optimization process to define the hydraulic geometry of the bifurcation was performed. The CFD results show the complexity of the flow through the bifurcation, especially under hydraulic short-circuit operation. Therefore, it was decided to perform experimental investigations in addition to the CFD analysis, in order to get a better understanding of the flow. The aim of these studies was to investigate the flow development upstream and downstream the bifurcation, the estimation of the bifurcation loss coefficients and also to provide comprehensive data of the flow behavior for the whole operating range of the machine. In order to evaluate the development of the velocity field Stereo Particle Image Velocimetry (S-PIV) measurements at different sections upstream and downstream of the bifurcation on the main penstock and Laser Doppler Anemometrie (LDA) measurements at bifurcation inlet were performed. This paper presents the CFD results obtained for the final design for different operating conditions, the model test procedures and the model test results with special attention to: 1) The bifurcation head loss coefficients, and their extrapolation to prototype conditions, 2) S-PIV and LDA measurements. Additionally, criteria to define the minimal uniformity conditions for the velocity profiles entering the turbine are evaluated. Finally, based on the gathered flow information a better understanding to define the preferred location of a bifurcation is gained and can be applied to future projects

Bovine aortic arch: A novel association with thoracic aortic dilation

International Nuclear Information System (INIS)

Malone, C.D.; Urbania, T.H.; Crook, S.E.S.; Hope, M.D.

2012-01-01

Aim: To investigate whether there is a link between bovine arch and thoracic aortic aneurysm. Materials and methods: Computed tomography (CT) and magnetic resonance imaging (MRI) images of the thorax of 191 patients with dilated thoracic aortas and 391 consecutive, unselected patients as controls were retrospectively reviewed. Bovine arch was considered present if either a shared origin of the left common carotid and innominate arteries or an origin of the left common carotid from the innominate artery was identified. A chi-square test was used to evaluate the significance of differences between subgroups. Results: A trend towards increased prevalence of bovine arch was seen in patients with dilated aortas (26.2%) compared to controls (20.5%, p = 0.12). The association was statistically significant in patients over 70 years old (31.9%, p = 0.019) and when dilation involved the aortic arch (47.6%, p = 0.003). Conclusions: An association between bovine arch and aortic dilation is seen in older patients, and when dilation involves the aortic arch. Bovine arch should be considered a potential risk factor for thoracic aortic aneurysm.

Energized Oxygen : Speiser Current Sheet Bifurcation

Science.gov (United States)

George, D. E.; Jahn, J. M.

2017-12-01

A single population of energized Oxygen (O+) is shown to produce a cross-tail bifurcated current sheet in 2.5D PIC simulations of the magnetotail without the influence of magnetic reconnection. Treatment of oxygen in simulations of space plasmas, specifically a magnetotail current sheet, has been limited to thermal energies despite observations of and mechanisms which explain energized ions. We performed simulations of a homogeneous oxygen background, that has been energized in a physically appropriate manner, to study the behavior of current sheets and magnetic reconnection, specifically their bifurcation. This work uses a 2.5D explicit Particle-In-a-Cell (PIC) code to investigate the dynamics of energized heavy ions as they stream Dawn-to-Dusk in the magnetotail current sheet. We present a simulation study dealing with the response of a current sheet system to energized oxygen ions. We establish a, well known and studied, 2-species GEM Challenge Harris current sheet as a starting point. This system is known to eventually evolve and produce magnetic reconnection upon thinning of the current sheet. We added a uniform distribution of thermal O+ to the background. This 3-species system is also known to eventually evolve and produce magnetic reconnection. We add one additional variable to the system by providing an initial duskward velocity to energize the O+. We also traced individual particle motion within the PIC simulation. Three main results are shown. First, energized dawn- dusk streaming ions are clearly seen to exhibit sustained Speiser motion. Second, a single population of heavy ions clearly produces a stable bifurcated current sheet. Third, magnetic reconnection is not required to produce the bifurcated current sheet. Finally a bifurcated current sheet is compatible with the Harris current sheet model. This work is the first step in a series of investigations aimed at studying the effects of energized heavy ions on magnetic reconnection. This work differs

Tissue Responses to Stent Grafts with Endo-Exo-Skeleton for Saccular Abdominal Aortic Aneurysms in a Canine Model

Energy Technology Data Exchange (ETDEWEB)

Kim, Il Young; Chung, Jin Wook; Kim, Hyo Cheol [Dept. of Radiology and Institute of Radiation Medicine, Seoul National University College of Medicine, Clinical Research Institute, Seoul (Korea, Republic of); Choi, Young Ho; So Young Ho [Dept. of Radiology, Seoul National University Boramae Hospital, Seoul (Korea, Republic of); Kim, Hyun Beom [Dept. of Radiology, National Cancer Center, Goyang (Korea, Republic of); Min, Seung Kee [Dept. of Surgery, Seoul National University College of Medicine, Seoul (Korea, Republic of); Park, Jae Hyung [Dept. of Radiology, Gachon University Gil Medical Center, Incheon (Korea, Republic of)

2014-10-15

We evaluated the effect of close contact between the stent and the graft on the induction of endothelial covering on the stent graft placed over an aneurysm. Saccular abdominal aortic aneurysms were made with Dacron patch in eight dogs. The stent graft consisted of an inner stent, a expanded polytetrafluoroethylene graft, and an outer stent. After sacrificing the animals, the aortas with an embedded stent graft were excised. The aortas were inspected grossly and evaluated microscopically. The animals were sacrificed at two (n = 3), six (n = 3), and eight months (n = 2) after endovascular repair. In two dogs, the aortic lumen was occluded at two months after the placement. On gross inspection of specimens from the other six dogs with a patent aortic lumen, stent grafts placed over the normal aortic wall were covered by glossy white neointima, whereas, stent grafts placed over the aneurysmal aortic wall were covered by brownish neointima. On microscopic inspection, stent grafts placed over the normal aortic wall were covered by thin neointima (0.27 ± 0.05 mm, mean ± standard deviation) with an endothelial layer, and stent grafts placed over the aneurysmal aortic wall were covered by thick neointima (0.62 ± 0.17 mm) without any endothelial lining. Transgraft cell migration at the normal aortic wall was more active than that at the aneurysmal aortic wall. Close contact between the stent and the graft, which was achieved with stent grafts with endo-exo-skeleton, could not enhance endothelial covering on the stent graft placed over the aneurysms.

USE OF COVERED SELF-EXPANDABLE NITINOL STENT FOR ANASTOMOTIC BILIARY STRUCTURE MANAGEMENT AFTER LIVER TRANSPLANTATION: THE FIRST EXPERIENCE

Directory of Open Access Journals (Sweden)

M. N. Kornilov

2013-01-01

Full Text Available Aim. The aim of this study focuses on the first experience with self-expandable stents, analysis of its efficacy and safety in the treatment of anastomotic strictures after liver transplantation. Materials and methods. There’re 136 liver transplantations performed from 2004 till 2012. To correct anastomotic strictures we’ve used only the self-expandable coated nitinol stent. We performed stenting in 7 recipient. Result. In 131 liver transplant recipients incidence of biliary strictures has been 5.3%. All of 5 patients have been managed by retrograde or antegrade way. Conclusion. Our first experience demonstrate efficacy and safety of the used tecniques up to 24 months. The analysis of more long-term results is required. 

Role of Self-Expandable Metal Stents in Acute Variceal Bleeding

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Fuad Maufa

2012-01-01

Full Text Available Acute variceal bleeding continues to be associated with significant mortality. Current standard of care combines hemodynamic stabilization, antibiotic prophylaxis, pharmacological agents, and endoscopic treatment. Rescue therapies using balloon tamponade or transjugular intrahepatic portosystemic shunt are implemented when first-line therapy fails. Rescue therapies have many limitations and are contraindicated in some cases. Placement of fully covered self-expandable metallic stent is a promising therapeutic technique that can be used to control bleeding in cases of refractory esophageal bleeding as an alternative to balloon tamponade. These stents can be left in place for as long as two weeks, allowing for improvement in liver function and institution of a more definitive treatment.

Clinical outcomes of self-expandable stent placement for benign esophageal diseases: A pooled analysis of the literature

Science.gov (United States)

van Halsema, Emo E; van Hooft, Jeanin E

2015-01-01

AIM: To analyze the outcomes of self-expandable stent placement for benign esophageal strictures and benign esophageal leaks in the literature. METHODS: The PubMed, Embase and Cochrane databases were searched for relevant articles published between January 2000 and July 2014. Eight prospective studies were identified that analyzed the outcomes of stent placement for refractory benign esophageal strictures. The outcomes of stent placement for benign esophageal leaks, perforations and fistulae were extracted from 20 retrospective studies that were published after the inclusion period of a recent systematic review. Data were pooled and analyzed using descriptive statistics. RESULTS: Fully covered self-expandable metal stents (FC SEMS) (n = 85), biodegradable (BD) stents (n = 77) and self-expandable plastic stents (SEPS) (n = 70) were inserted in 232 patients with refractory benign esophageal strictures. The overall clinical success rate was 24.2% and according to stent type 14.1% for FC SEMS, 32.9% for BD stents and 27.1% for SEPS. Stent migration occurred in 24.6% of cases. The overall complication rate was 31.0%, including major (17.7%) and minor (13.4%) complications. A total of 643 patients were treated with self-expandable stents mainly for postsurgical leaks (64.5%), iatrogenic perforations (19.6%), Boerhaave’s syndrome (7.8%) and fistulae (3.7%). FC SEMS and partially covered SEMS were used in the majority of patients. Successful closure of the defect was achieved in 76.8% of patients and according to etiology in 81.4% for postsurgical leaks, 86.0% for perforations and 64.7% for fistulae. The pooled stent migration rate was 16.5%. Stent-related complications occurred in 13.4% of patients, including major (7.8%) and minor (5.5%) complications. CONCLUSION: The outcomes of stent placement for refractory benign esophageal strictures were poor. However, randomized trials are needed to put this into perspective. The evidence on successful stent placement for benign

Clinical outcomes of self-expandable stent placement for benign esophageal diseases: A pooled analysis of the literature.

Science.gov (United States)

van Halsema, Emo E; van Hooft, Jeanin E

2015-02-16

To analyze the outcomes of self-expandable stent placement for benign esophageal strictures and benign esophageal leaks in the literature. The PubMed, Embase and Cochrane databases were searched for relevant articles published between January 2000 and July 2014. Eight prospective studies were identified that analyzed the outcomes of stent placement for refractory benign esophageal strictures. The outcomes of stent placement for benign esophageal leaks, perforations and fistulae were extracted from 20 retrospective studies that were published after the inclusion period of a recent systematic review. Data were pooled and analyzed using descriptive statistics. Fully covered self-expandable metal stents (FC SEMS) (n = 85), biodegradable (BD) stents (n = 77) and self-expandable plastic stents (SEPS) (n = 70) were inserted in 232 patients with refractory benign esophageal strictures. The overall clinical success rate was 24.2% and according to stent type 14.1% for FC SEMS, 32.9% for BD stents and 27.1% for SEPS. Stent migration occurred in 24.6% of cases. The overall complication rate was 31.0%, including major (17.7%) and minor (13.4%) complications. A total of 643 patients were treated with self-expandable stents mainly for postsurgical leaks (64.5%), iatrogenic perforations (19.6%), Boerhaave's syndrome (7.8%) and fistulae (3.7%). FC SEMS and partially covered SEMS were used in the majority of patients. Successful closure of the defect was achieved in 76.8% of patients and according to etiology in 81.4% for postsurgical leaks, 86.0% for perforations and 64.7% for fistulae. The pooled stent migration rate was 16.5%. Stent-related complications occurred in 13.4% of patients, including major (7.8%) and minor (5.5%) complications. The outcomes of stent placement for refractory benign esophageal strictures were poor. However, randomized trials are needed to put this into perspective. The evidence on successful stent placement for benign esophageal leaks, perforations and

FFT Bifurcation Analysis of Routes to Chaos via Quasiperiodic Solutions

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L. Borkowski

2015-01-01

Full Text Available The dynamics of a ring of seven unidirectionally coupled nonlinear Duffing oscillators is studied. We show that the FFT analysis presented in form of a bifurcation graph, that is, frequency distribution versus a control parameter, can provide a valuable and helpful complement to the corresponding typical bifurcation diagram and the course of Lyapunov exponents, especially in context of detailed identification of the observed attractors. As an example, bifurcation analysis of routes to chaos via 2-frequency and 3-frequency quasiperiodicity is demonstrated.

Aortic Root Surgery in Marfan Syndrome: Medium-Term Outcome in a Single-Center Experience.

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Attenhofer Jost, Christine H; Connolly, Heidi M; Scott, Christopher G; Ammash, Naser M; Bowen, Juan M; Schaff, Hartzell V

2017-01-01

The study aim was to analyze the authors' experience with aortic root surgery in Marfan syndrome (MFS), and to expand the surgical outcome data of patients meeting the Ghent criteria (Marfan registry). Analyses were performed of data acquired from MFS patients (who met the Ghent criteria), including an aortic root surgery and Kaplan-Meier survival. Between April 2004 and February 2012, a total of 59 MFS patients (mean age at surgery 36 ± 13 years) underwent 67 operations for aortic root aneurysm (n = 52), aortic valve (AV) regurgitation (n = 15), acute aortic dissection (n = 2), and/or mitral valve (MV) regurgitation resulting from MV prolapse (n = 7). Of 59 initial operations, 21 (36%) involved AV-replacing root surgery, 38 (64%) AV-sparing root surgery, seven (12%) aortic arch or hemi-arch repair, and five (8%) simultaneous MV surgery. There were no early mortalities. The mean follow up was 6.8 ± 1.2 years, with five deaths (8%) and a relatively low reoperation rate (10 reoperations in nine patients; 14%). Seven reoperations involved AV or aortic root surgery (including four for AV regurgitation following failed AV-sparing surgery), two MV repair/replacements, and one coronary artery bypass graft. Eight patients (21%) with AV-sparing surgery had moderate/severe AV regurgitation at the last follow up before re-intervention. The mean five-year freedom from postoperative death was 91.2 ± 8.8%, from cardiac reoperation 86.3 ± 4.5%, and more-than-moderate AV regurgitation 90.3 ± 4.8%. Prophylactic aortic surgery in MFS patients with AV-replacing root or AV-sparing root surgery carries a low risk of operative morbidity and death when performed at an experienced center. AV-sparing root surgery increases the risk of AV regurgitation and, possibly, of re-intervention. Regular clinical follow up is important after any aortic root surgery in MFS patients, with a delineation of risk factors for AV regurgitation after AV rootsparing surgery.

EXPERIMENTAL STUDY ON SEDIMENT DISTRIBUTION AT CHANNEL BIFURCATION

Institute of Scientific and Technical Information of China (English)

G.M. Tarekul ISLAM; M.R. KABIR; Ainun NISHAT

2002-01-01

This paper presents the experimental results on the distribution of sediments at channel bifurcation.The experiments have been conducted in a physical model of channel bifurcation. It consists of a straight main channel which bifurcates into two branch channels of different widths. The test rig is a mobile bed with fixed bank. Four different noses have been used to study the phenomenon. For each nose, three upstream discharges viz. 20 l/s, 30 l/s and 40 l/s have been employed. From the measured data, discharges and sediment transport ratios per unit width are calculated in the downstream branches.These data have been set to the general nodal point relation and a set of equations has been developed to describe the distribution of sediments to the downstream branches for different nose angles.

Valve thrombosis following transcatheter aortic valve implantation: a systematic review.

Science.gov (United States)

Córdoba-Soriano, Juan G; Puri, Rishi; Amat-Santos, Ignacio; Ribeiro, Henrique B; Abdul-Jawad Altisent, Omar; del Trigo, María; Paradis, Jean-Michel; Dumont, Eric; Urena, Marina; Rodés-Cabau, Josep

2015-03-01

Despite the rapid global uptake of transcatheter aortic valve implantation, valve trombosis has yet to be systematically evaluated in this field. The aim of this study was to determine the clinical characteristics, diagnostic criteria, and treatment outcomes of patients diagnosed with valve thrombosis following transcatheter aortic valve implantation through a systematic review of published data. Literature published between 2002 and 2012 on valve thrombosis as a complication of transcatheter aortic valve implantation was identified through a systematic electronic search. A total of 11 publications were identified, describing 16 patients (mean age, 80 [5] years, 65% men). All but 1 patient (94%) received a balloon-expandable valve. All patients received dual antiplatelet therapy immediately following the procedure and continued to take either mono- or dual antiplatelet therapy at the time of valve thrombosis diagnosis. Valve thrombosis was diagnosed at a median of 6 months post-procedure, with progressive dyspnea being the most common symptom. A significant increase in transvalvular gradient (from 10 [4] to 40 [12] mmHg) was the most common echocardiographic feature, in addition to leaflet thickening. Thrombus was not directly visualized with echocardiography. Three patients underwent valve explantation, and the remaining received warfarin, which effectively restored the mean transvalvular gradient to baseline within 2 months. Systemic embolism was not a feature of valve thrombosis post-transcatheter aortic valve implantation. Although a rare, yet likely under-reported complication of post-transcatheter aortic valve implantation, progressive dyspnea coupled with an increasing transvalvular gradient on echocardiography within the months following the intervention likely signifies valve thrombosis. While direct thrombus visualization appears difficult, prompt initiation of oral anticoagulation therapy effectively restores baseline valve function. Copyright © 2014

Predictors of the patency of self-expandable metallic stents in malignant gastroduodenal obstruction.

Science.gov (United States)

Kim, Seung Han; Chun, Hoon Jai; Yoo, In Kyung; Lee, Jae Min; Nam, Seung Joo; Choi, Hyuk Soon; Kim, Eun Sun; Keum, Bora; Seo, Yeon Seok; Jeen, Yoon Tae; Lee, Hong Sik; Um, Soon Ho; Kim, Chang Duck

2015-08-14

To investigate the predictive factors of self-expandable metallic stent patency after stent placement in patients with inoperable malignant gastroduodenal obstruction. A total of 116 patients underwent stent placements for inoperable malignant gastroduodenal obstruction at a tertiary academic center. Clinical success was defined as acceptable decompression of the obstructive lesion within the malignant gastroduodenal neoplasm. We evaluated patient comorbidities and clinical statuses using the World Health Organization's scoring system and categorized patient responses to chemotherapy using the Response Evaluation Criteria in Solid Tumors criteria. We analyzed the relationships between possible predictive factors and stent patency. Self-expandable metallic stent placement was technically successful in all patients (100%), and the clinical success rate was 84.2%. In a multivariate Cox proportional hazards model, carcinoembryonic antigen (CEA) levels were correlated with a reduction in stent patency [P = 0.006; adjusted hazard ratio (aHR) = 2.92, 95%CI: 1.36-6.25]. Palliative chemotherapy was statistically associated with an increase in stent patency (P = 0.009; aHR = 0.27, 95%CI: 0.10-0.72). CEA levels can easily be measured at the time of stent placement and may help clinicians to predict stent patency and determine the appropriate stent procedure.

Long-term results of percutaneous self-expandable metallic stents in malignant biliary obstruction

International Nuclear Information System (INIS)

Kobashi, Yuko; Hoshikawa, Yoshikazu

2004-01-01

Evaluation of the long-term follow-up data of 155 patients with inoperable malignant biliary obstruction who received percutaneous placement of self expandable metallic stent (EMS) and external beam radiotherapy (EBR) combined with self-expandable metallic stent. One-hundred sixty EMS were inserted in 155 patients with inoperable malignant biliary obstruction. One-hundred forty-three patients (Group A) were inserted EMS alone. Twelve patients (Group B) underwent external radiotherapy (40∼45 Gy) after stent insertion. We compared to the Group A and Group B about survival, stent patency and administration. The mean length of survival for the entire group was 111±87 days, while the mean period of patency for all stents was 103±74. We found no statistically significant difference in patient survival or stent patency periods in regard to the level and cause of obstruction. Prolongation of actuarial survival was observed in Group B (316±231 days) as compared to Group A (126±85 days,). Mean length of survival rate and mean period of stent patency rate were not significantly different in regard to the level, cause of obstruction and each stent. External radiotherapy combined EMS could achieve effective palliation and improve the quality of life in selected patients with malignant biliary obstruction. (author)

Long-Term Results After Simple Versus Complex Stenting of Coronary Artery Bifurcation Lesions Nordic Bifurcation Study 5-Year Follow-Up Results

DEFF Research Database (Denmark)

Maeng, M.; Holm, N. R.; Erglis, A.

2013-01-01

Objectives This study sought to report the 5-year follow-up results of the Nordic Bifurcation Study. Background Randomized clinical trials with short-term follow-up have indicated that coronary bifurcation lesions may be optimally treated using the optional side branch stenting strategy. Methods...... complex strategy of planned stenting of both the main vessel and the side branch. (C) 2013 by the American College of Cardiology Foundation...

Hopf bifurcations of a ratio-dependent predator–prey model involving two discrete maturation time delays

International Nuclear Information System (INIS)

Karaoglu, Esra; Merdan, Huseyin

2014-01-01

Highlights: • A ratio-dependent predator–prey system involving two discrete maturation time delays is studied. • Hopf bifurcations are analyzed by choosing delay parameters as bifurcation parameters. • When a delay parameter passes through a critical value, Hopf bifurcations occur. • The direction of bifurcation, the period and the stability of periodic solution are also obtained. - Abstract: In this paper we give a detailed Hopf bifurcation analysis of a ratio-dependent predator–prey system involving two different discrete delays. By analyzing the characteristic equation associated with the model, its linear stability is investigated. Choosing delay terms as bifurcation parameters the existence of Hopf bifurcations is demonstrated. Stability of the bifurcating periodic solutions is determined by using the center manifold theorem and the normal form theory introduced by Hassard et al. Furthermore, some of the bifurcation properties including direction, stability and period are given. Finally, theoretical results are supported by some numerical simulations

Magneto-elastic dynamics and bifurcation of rotating annular plate*

International Nuclear Information System (INIS)

Hu Yu-Da; Piao Jiang-Min; Li Wen-Qiang

2017-01-01

In this paper, magneto-elastic dynamic behavior, bifurcation, and chaos of a rotating annular thin plate with various boundary conditions are investigated. Based on the thin plate theory and the Maxwell equations, the magneto-elastic dynamic equations of rotating annular plate are derived by means of Hamilton’s principle. Bessel function as a mode shape function and the Galerkin method are used to achieve the transverse vibration differential equation of the rotating annular plate with different boundary conditions. By numerical analysis, the bifurcation diagrams with magnetic induction, amplitude and frequency of transverse excitation force as the control parameters are respectively plotted under different boundary conditions such as clamped supported sides, simply supported sides, and clamped-one-side combined with simply-anotherside. Poincaré maps, time history charts, power spectrum charts, and phase diagrams are obtained under certain conditions, and the influence of the bifurcation parameters on the bifurcation and chaos of the system is discussed. The results show that the motion of the system is a complicated and repeated process from multi-periodic motion to quasi-period motion to chaotic motion, which is accompanied by intermittent chaos, when the bifurcation parameters change. If the amplitude of transverse excitation force is bigger or magnetic induction intensity is smaller or boundary constraints level is lower, the system can be more prone to chaos. (paper)

"Stent" auto-expansível nas dissecções da aorta tipo B Self-expanding stent in type B dissections of the aorta

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Wagner Michael PEREIRA

1999-07-01

Full Text Available O tratamento clínico das dissecções agudas da aorta do tipo B tem mortalidade em torno de 25% menor que a mortalidade cirúrgica. O tratamento cirúrgico das dissecções crônicas também produz uma morbidade e mortalidade elevadas. A utilização de "stents"auto-expansíveis endovasculares pode ser uma nova alternativa no tratamento destas lesões. De abril a dezembro de 1998 foram implantados 15 "stents" endovasculares, 10 em dissecções agudas e 5 em crônicas. A idade dos pacientes variou entre 48 e 75 anos (média=60,53±9,73 anos com 66,6% do sexo masculino. Os pacientes foram submetidos à esternotomia mediana, circulação extracorpórea (CEC com hipotermia profunda (18° - 20°C, parada circulatória total (PCT e perfusão cerebral retrógrada (PCR. A aorta transversa foi incisada e implantado o "stent" na aorta descendente sob auxílio de aortoscopia. Foram analisados os tempos de CEC, pinçamento aórtico, PCT, PCR, reaquecimento, ventilação mecânica, internação, sangramento trans e pós-operatório, reposição sangüínea, gasometria, curva de eventos e sobrevida. A mortalidade hospitalar (30 dias foi de 6,6%; 2 pacientes foram reoperados com 3 e 6 meses após a operação com dissecção da aorta ascendente e aneurisma roto distal ao "stent". Quatorze vêm sendo acompanhados com 1 a 8m de evolução, sendo que 85,7% estão livres de eventos e curva de sobrevida de 93,1%(240 dias. Concluímos que o implante de "stent"intraluminais auto-expansíveis apresentou mortalidade menor na fase aguda da doença (6,6% comparada à nossa experiência anterior com o tratamento clínico (30%. Apesar da amostra ser pequena, o procedimento parece ser promissor e necessita mais acompanhamento.The clinical treatment of acute type B aortic dissection has a mortality of about 25%, therefore, less than surgical mortality. The surgical treatment of chronic dissections also produces a high morbidity and mortality. The use of self-expanding

Bifurcation Analysis of the QI 3-D Four-Wing Chaotic System

International Nuclear Information System (INIS)

Sun, Y.; Qi, G.; Wang, Z.; Wyk, B.J. van

2010-01-01

This paper analyzes the pitchfork and Hopf bifurcations of a new 3-D four-wing quadratic autonomous system proposed by Qi et al. The center manifold technique is used to reduce the dimensions of this system. The pitchfork and Hopf bifurcations of the system are theoretically analyzed. The influence of system parameters on other bifurcations are also investigated. The theoretical analysis and simulations demonstrate the rich dynamics of the system. (authors)

Bifurcation Control of an Electrostatically-Actuated MEMS Actuator with Time-Delay Feedback

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Lei Li

2016-10-01

Full Text Available The parametric excitation system consisting of a flexible beam and shuttle mass widely exists in microelectromechanical systems (MEMS, which can exhibit rich nonlinear dynamic behaviors. This article aims to theoretically investigate the nonlinear jumping phenomena and bifurcation conditions of a class of electrostatically-driven MEMS actuators with a time-delay feedback controller. Considering the comb structure consisting of a flexible beam and shuttle mass, the partial differential governing equation is obtained with both the linear and cubic nonlinear parametric excitation. Then, the method of multiple scales is introduced to obtain a slow flow that is analyzed for stability and bifurcation. Results show that time-delay feedback can improve resonance frequency and stability of the system. What is more, through a detailed mathematical analysis, the discriminant of Hopf bifurcation is theoretically derived, and appropriate time-delay feedback force can make the branch from the Hopf bifurcation point stable under any driving voltage value. Meanwhile, through global bifurcation analysis and saddle node bifurcation analysis, theoretical expressions about the system parameter space and maximum amplitude of monostable vibration are deduced. It is found that the disappearance of the global bifurcation point means the emergence of monostable vibration. Finally, detailed numerical results confirm the analytical prediction.

Reverse extra-anatomic aortic arch debranching procedure allowing thoracic endovascular aortic repair of a chronic ascending aortic aneurysm

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Ludovic Canaud, MD, PhD

2018-06-01

Full Text Available A 79-year-old woman was admitted with a large chronic dissecting ascending aortic aneurysm starting 5 mm distal to the ostia of the left coronary artery and ending immediately proximal to the innominate artery. A reverse extra-anatomic aortic arch debranching procedure was performed. During the same operative time, through a transapical approach, a thoracic stent graft was deployed with the proximal landing zone just distal to the coronary ostia and the distal landing zone excluding the origin of the left common carotid artery. The postoperative course was uneventful. Computed tomography at 12 months documented patent extra-anatomic aortic arch debranching and no evidence of endoleak. Keywords: Ascending aorta, Thoracic aorta, Aortic dissection, Stent graft

Retrograde ascending aortic dissection during or after thoracic aortic stent graft placement: insight from the European registry on endovascular aortic repair complications

DEFF Research Database (Denmark)

Eggebrecht, Holger; Thompson, Matt; Rousseau, Hervé

2009-01-01

BACKGROUND: Single-center reports have identified retrograde ascending aortic dissection (rAAD) as a potentially lethal complication of thoracic endovascular aortic repair (TEVAR). METHODS AND RESULTS: Between 1995 and 2008, 28 centers participating in the European Registry on Endovascular Aortic...

Local stability and Hopf bifurcation in small-world delayed networks

International Nuclear Information System (INIS)

Li Chunguang; Chen Guanrong

2004-01-01

The notion of small-world networks, recently introduced by Watts and Strogatz, has attracted increasing interest in studying the interesting properties of complex networks. Notice that, a signal or influence travelling on a small-world network often is associated with time-delay features, which are very common in biological and physical networks. Also, the interactions within nodes in a small-world network are often nonlinear. In this paper, we consider a small-world networks model with nonlinear interactions and time delays, which was recently considered by Yang. By choosing the nonlinear interaction strength as a bifurcation parameter, we prove that Hopf bifurcation occurs. We determine the stability of the bifurcating periodic solutions and the direction of the Hopf bifurcation by applying the normal form theory and the center manifold theorem. Finally, we show a numerical example to verify the theoretical analysis

Local stability and Hopf bifurcation in small-world delayed networks

Energy Technology Data Exchange (ETDEWEB)

Li Chunguang E-mail: cgli@uestc.edu.cn; Chen Guanrong E-mail: gchen@ee.cityu.edu.hk

2004-04-01

The notion of small-world networks, recently introduced by Watts and Strogatz, has attracted increasing interest in studying the interesting properties of complex networks. Notice that, a signal or influence travelling on a small-world network often is associated with time-delay features, which are very common in biological and physical networks. Also, the interactions within nodes in a small-world network are often nonlinear. In this paper, we consider a small-world networks model with nonlinear interactions and time delays, which was recently considered by Yang. By choosing the nonlinear interaction strength as a bifurcation parameter, we prove that Hopf bifurcation occurs. We determine the stability of the bifurcating periodic solutions and the direction of the Hopf bifurcation by applying the normal form theory and the center manifold theorem. Finally, we show a numerical example to verify the theoretical analysis.

Iterative Controller Tuning for Process with Fold Bifurcations

DEFF Research Database (Denmark)

Huusom, Jakob Kjøbsted; Poulsen, Niels Kjølstad; Jørgensen, Sten Bay

2007-01-01

Processes involving fold bifurcation are notoriously difficult to control in the vicinity of the fold where most often optimal productivity is achieved . In cases with limited process insight a model based control synthesis is not possible. This paper uses a data driven approach with an improved...... version of iterative feedback tuning to optimizing a closed loop performance criterion, as a systematic tool for tuning process with fold bifurcations....

Expand Your Horizon: A programme that improves body image and reduces self-objectification by training women to focus on body functionality.

Science.gov (United States)

Alleva, Jessica M; Martijn, Carolien; Van Breukelen, Gerard J P; Jansen, Anita; Karos, Kai

2015-09-01

This study tested Expand Your Horizon, a programme designed to improve body image by training women to focus on the functionality of their body using structured writing assignments. Eighty-one women (Mage=22.77) with a negative body image were randomised to the Expand Your Horizon programme or to an active control programme. Appearance satisfaction, functionality satisfaction, body appreciation, and self-objectification were measured at pretest, posttest, and one-week follow-up. Following the intervention, participants in the Expand Your Horizon programme experienced greater appearance satisfaction, functionality satisfaction, and body appreciation, and lower levels of self-objectification, compared to participants in the control programme. Partial eta-squared effect sizes were of small to medium magnitude. This study is the first to show that focusing on body functionality can improve body image and reduce self-objectification in women with a negative body image. These findings provide support for addressing body functionality in programmes designed to improve body image. Copyright © 2015 Elsevier Ltd. All rights reserved.

Efficacy of a Self-Expandable Porous Stent as the Sole Curative Treatment for Extracranial Carotid Pseudoaneurysms.

Science.gov (United States)

Chen, Peng Roc; Edwards, Nancy J; Sanzgiri, Aditya; Day, Arthur L

2016-04-01

Extracranial carotid pseudoaneurysms are uncommon vascular lesions. Even with conservative management complications can happen, such as delayed cerebral embolization or symptoms due to flow limitation. Although endovascular therapy can be curative, literature demonstrating a preferred technique is scant. Our goal was to evaluate the use of 1 technique only-the deployment of overlapping self-expandable porous stents-to treat a series of extracranial carotid pseudoaneurysms. From 2008 to 2014, 14 consecutive cases of symptomatic extracranial carotid pseudoaneurysms were managed with single or multilayer porous stents at our institution. Each patient underwent a standardized angiographic follow-up at 6 months. Twelve patients also received a follow-up computed tomography angiogram at 12 months, and yearly thereafter (median radiographic follow-up, 38 months). The total clinical follow-up period ranged between 6 and 69 months (median, 46 months). In our series, each of the extracranial carotid pseudoaneurysms appeared to be the result of carotid artery dissection with associated carotid stenosis at the origin of every pseudoaneurysm. Endovascular treatment consisted of 1-3 layers of self-expandable porous stents placed without balloon angioplasty. Immediately after stenting angiographic images were notable for stagnant opacification of the pseudoaneurysm through the stent(s). All pseudoaneurysms were completely obliterated by the 6-month follow-up angiogram and remained so throughout the radiographic follow-up period. Complications were minimal, consisting of 1 patient developing a mild Horner's syndrome after treatment that resolved during clinical follow-up. Extracranial carotid pseudoaneurysms can be successfully obliterated with the use of porous, self-expandable stents. Copyright © 2016 Elsevier Inc. All rights reserved.

Nonresonant Double Hopf Bifurcation in Toxic Phytoplankton-Zooplankton Model with Delay

Science.gov (United States)

Yuan, Rui; Jiang, Weihua; Wang, Yong

This paper investigates a toxic phytoplankton-zooplankton model with Michaelis-Menten type phytoplankton harvesting. The model has rich dynamical behaviors. It undergoes transcritical, saddle-node, fold, Hopf, fold-Hopf and double Hopf bifurcation, when the parameters change and go through some of the critical values, the dynamical properties of the system will change also, such as the stability, equilibrium points and the periodic orbit. We first study the stability of the equilibria, and analyze the critical conditions for the above bifurcations at each equilibrium. In addition, the stability and direction of local Hopf bifurcations, and the completion bifurcation set by calculating the universal unfoldings near the double Hopf bifurcation point are given by the normal form theory and center manifold theorem. We obtained that the stable coexistent equilibrium point and stable periodic orbit alternate regularly when the digestion time delay is within some finite value. That is, we derived the pattern for the occurrence, and disappearance of a stable periodic orbit. Furthermore, we calculated the approximation expression of the critical bifurcation curve using the digestion time delay and the harvesting rate as parameters, and determined a large range in terms of the harvesting rate for the phytoplankton and zooplankton to coexist in a long term.

Hybrid treatment of a true thyreocervical trunk aneurysm in a patient with Type B aortic dissection

Directory of Open Access Journals (Sweden)

Nikolaos G Baikoussis

2016-01-01

Full Text Available We would like to describe a case with a complex aortic disease treated in hybrid fashion. We present an interesting case of a 65-year-old man with a medical history of hypertension, hyperlipidemia, and coronary artery disease percutaneously treated. An acute Type B aortic dissection occurred and treated with the implantation of a stent-graft which occluded the left subclavian artery due to its extension to the aortic arch. This event required a carotid-subclavian artery bypass due to ischemia of the left arm. An aneurysm in the innominate artery also detected, was treated with another stent-graft implantation 3 months later. At 5-year follow-up, an aneurysm of the thyreocervical trunk was found while the stent-graft of the aorta was well-tolerated without endoleak and the carotid-subclavian graft was patent. The aneurysm was asymptomatic but considering the risk of spontaneous rupture of an aneurysm of this size, elective surgery was indicated. Because the aneurysm was very close to the brachiocephalic bifurcation, open surgical repair would require a sternotomy. The right common carotid artery and right subclavian artery were exposed. The thyrocervical trunk, right internal mammary artery and right vertebral artery were occluded by ligations to isolate the aneurysm. An 8-mm Dacron graft was anastomosed end-to-end to the distal part of subclavian artery. We would like through this case, discuss the role of the hybrid cardiovascular surgery to minimize the postoperative complications in complex cardiovascular pathology. We also discuss the international bibliography about the thyreocervical trunk aneurysm and the treatment options.

Transcatheter aortic valve replacement: historical perspectives, current evidence, and future directions.

Science.gov (United States)

Horne, Aaron; Reineck, Elizabeth A; Hasan, Rani K; Resar, Jon R; Chacko, Matthews

2014-10-01

Severe aortic stenosis (AS) results in considerable morbidity and mortality without aortic valve replacement and is expected to increase in prevalence with the aging population. Because AS primarily affects the elderly, many patients with comorbidities are poor candidates for surgical aortic valve replacement (SAVR) and may not be referred. Transcatheter aortic valve replacement (TAVR) has emerged as transformative technology for the management of AS over the past decade. Randomized trials have established the safety and efficacy of TAVR with improved mortality and quality of life compared with medical therapy in inoperable patients, while demonstrating noninferiority and even superiority to SAVR among high-risk operative candidates. However, early studies demonstrated an early penalty of stroke and vascular complications with TAVR as well as increased paravalvular leak as compared with SAVR. Two device platforms have been evaluated and approved for use in the United States: the Edwards SAPIEN and the Medtronic CoreValve. Early studies also suggest cost-effectiveness for TAVR. Ongoing studies are evaluating new iterations of the aforementioned TAVR devices, novel device designs, and applications of TAVR in expanded populations of patients including those with lower risk profiles as well as those with comorbidities that were excluded from early clinical trials. Future improvements in TAVR technology will likely reduce periprocedural and long-term complications. Further studies are needed to confirm device durability over long-term follow-up and explore the applicability of TAVR to broader AS patient populations. Copyright © 2014 Mosby, Inc. All rights reserved.

Geometric Deformations of the Thoracic Aorta and Supra-Aortic Arch Branch Vessels Following Thoracic Endovascular Aortic Repair.

Science.gov (United States)

Ullery, Brant W; Suh, Ga-Young; Hirotsu, Kelsey; Zhu, David; Lee, Jason T; Dake, Michael D; Fleischmann, Dominik; Cheng, Christopher P

2018-04-01

To utilize 3-D modeling techniques to better characterize geometric deformations of the supra-aortic arch branch vessels and descending thoracic aorta after thoracic endovascular aortic repair. Eighteen patients underwent endovascular repair of either type B aortic dissection (n = 10) or thoracic aortic aneurysm (n = 8). Computed tomography angiography was obtained pre- and postprocedure, and 3-D geometric models of the aorta and supra-aortic branch vessels were constructed. Branch angle of the supra-aortic branch vessels and curvature metrics of the ascending aorta, aortic arch, and stented thoracic aortic lumen were calculated both at pre- and postintervention. The left common carotid artery branch angle was lower than the left subclavian artery angles preintervention ( P Supra-aortic branch vessel angulation remains relatively static when proximal landing zones are distal to the left common carotid artery.

Polyurethane-Covered Self-expandable Nitinol Stent for Malignant Biliary Obstruction: Preliminary Results

International Nuclear Information System (INIS)

Han, Young-Min; Hwang, Seung-Bae; Lee, Soo-Teik; Lee, Jeong-Min; Chung, Gyung-Ho

2002-01-01

Purpose: To evaluate the immediate and long-term results in ten patients with malignant biliary obstruction using a polyurethane-covered, self-expandable nitinol stent.Methods: A nitinol stent, fully covered with high-elasticity polyurethane, with an unconstrained diameter of 10 mm and a total length of 60-80 mm, was placed transhepatically under fluoroscopic guidance in ten patients. The length of the biliary obstruction varied between 30-50 mm. The follow-up examination included a clinical assessment, serum bilirubin measurement, and ultrasound examinations at one-month intervals in all patients. Results: Initial stent deployment was successful in eight patients. Two patients experienced proximal migration,which was solved by insertion of two, uncovered Wallstents. One patient had the stent removed after two weeks because of severe nausea and vomiting. One patient had delayed migration of the covered stent after 40 weeks. The follow-up duration was 3-40 weeks (Mean: 16.9 weeks). Seven patients died(3-26 weeks) and three patients survived (24-40 weeks). The bilirubin measurements in all patients had significantly decreased one week after stent insertion. The levels of amylase and lipase had did not increase after stent insertion. Conclusions: Apolyurethane-covered, self-expandable nitinol stent can be used effectively and safely in the treatment of malignant biliary obstruction. The preliminary results are favorable, but there is a need for further large studies to determine both long-term survival and patency

Dysphagia with malignant stricture of esophagogastric junction: treatment with self-expandable nitinol stent

International Nuclear Information System (INIS)

Lee, Choon Hyeong; Oh, Joo Hyeong; Yoon, Yup

1995-01-01

To evaluate the effectiveness, patency and safety of a self-expandable nitinol stent for palliative treatment of malignant stricture of gastroesophageal junction. An esophageal stent was inserted in five consecutive patients with malignant stricture of esophagogastric junction. Histologically, four cases were adenocarcinoma, and one was squamous cell carcinoma. The location and severity of stricture were evaluated with gastrografin just before stent insertion. In one patient with past subtotal gastrectomy, esophagography revealed fistulous fract at stricture site. No technical failure or procedural complications occurred, and improvement of dysphagia was noted in all patients soon after stent insertion. On follow up esophagograms performed 3 to 7 days after stent insertion, all stents were completely expanded and unchanged in positions. In one patient with fistulous connection at stricture site, esophagogram immediately after the procedure revealed complete occlusion of the fistula. Three patients died within 4, 7 and 8 consecutive months after stent insertion. Two patients are alive maintaining adequate body weight and passing most diet. Seft-expandable nitinol stent with it's good longitudinal flexibility and efficient radial force was effective in the palliative treatment of dysphagia in patient with malignant stricture at esophagogastric junction

Dysphagia with malignant stricture of esophagogastric junction: treatment with self-expandable nitinol stent

Energy Technology Data Exchange (ETDEWEB)

Lee, Choon Hyeong; Oh, Joo Hyeong; Yoon, Yup [Kyung Hee University Hospital, Seoul (Korea, Republic of)

1995-02-15

To evaluate the effectiveness, patency and safety of a self-expandable nitinol stent for palliative treatment of malignant stricture of gastroesophageal junction. An esophageal stent was inserted in five consecutive patients with malignant stricture of esophagogastric junction. Histologically, four cases were adenocarcinoma, and one was squamous cell carcinoma. The location and severity of stricture were evaluated with gastrografin just before stent insertion. In one patient with past subtotal gastrectomy, esophagography revealed fistulous fract at stricture site. No technical failure or procedural complications occurred, and improvement of dysphagia was noted in all patients soon after stent insertion. On follow up esophagograms performed 3 to 7 days after stent insertion, all stents were completely expanded and unchanged in positions. In one patient with fistulous connection at stricture site, esophagogram immediately after the procedure revealed complete occlusion of the fistula. Three patients died within 4, 7 and 8 consecutive months after stent insertion. Two patients are alive maintaining adequate body weight and passing most diet. Seft-expandable nitinol stent with it's good longitudinal flexibility and efficient radial force was effective in the palliative treatment of dysphagia in patient with malignant stricture at esophagogastric junction.

Aortic obstruction: anatomy and echocardiography

Directory of Open Access Journals (Sweden)

Keirns Candace

2006-09-01

Full Text Available Abstract Echocardiography is a valuable non-invasive technique for identifying the site and type of aortic obstruction. Knowledge of the morphological details of each type of obstruction is the basis for correct interpretation of the diagnostic images and clinical decisions. This study was undertaken to correlate the echocardiographic images with anatomic specimens of equivalent valvular and supravalvular aortic obstruction. Specimens were part of the collection of the Department of Embryology. Fifty six patients were studied, and forty specimens with aortic obstruction were analyzed. Echocardiographic characteristics: Thirty one (55.3% patients were women and twenty five (44.7% men. Valvular aortic obstruction was found in Thirty six patients (64.3 % and supravalvular aortic obstruction in twenty (35.7%. Anatomic characteristics: Of the forty specimens examined, twenty one (52.5% had valvular aortic obstruction and nineteen (47.5% supravalvular aortic obstruction. The anatomoechocardiographic correlation clearly showed that the anatomic findings of the specimen hearts and aortas corresponded to echocardiographic images of valvular and supravalvular aortic obstruction and provided solid corroboration of echocardiographic diagnoses.

Investigation of pitchfork bifurcation phenomena effects on heat transfer of viscoelastic flow inside a symmetric sudden expansion

Science.gov (United States)

Shahbani-Zahiri, A.; Hassanzadeh, H.; Shahmardan, M. M.; Norouzi, M.

2017-11-01

In this paper, the inertial and non-isothermal flows of the viscoelastic fluid through a planar channel with symmetric sudden expansion are numerically simulated. Effects of pitchfork bifurcation phenomena on the heat transfer rate are examined for the thermally developing and fully developed flow of the viscoelastic fluid inside the expanded part of the planar channel with an expansion ratio of 1:3. The rheological model of exponential Phan Thien-Tanner is used to include both the effects of shear-thinning and elasticity in fluid viscosity. The properties of fluids are temperature-dependent, and the viscous dissipation and heat stored by fluid elasticity are considered in the heat transfer equation. For coupling the governing equations, the PISO algorithm (Pressure Implicit with Splitting of Operator) is applied and the system of equations is linearized using the finite volume method on the collocated grids. The main purpose of this study is to examine the pitchfork bifurcation phenomena and its influences on the temperature distribution, the local and mean Nusselt numbers, and the first and second normal stress differences at different Reynolds, elasticity, and Brinkman numbers. The results show that by increasing the Brinkman number for the heated flow of the viscoelastic fluid inside the expanded part of the channel, the value of the mean Nusselt number is almost linearly decreased. Also, the maximum values of the local Nusselt number for the thermally developing flow and the local Nusselt number of the thermally fully developed flow are decremented by enhancing the Brinkman number.

Numerical bifurcation analysis of a class of nonlinear renewal equations

NARCIS (Netherlands)

Breda, Dimitri; Diekmann, Odo; Liessi, Davide; Scarabel, Francesca

2016-01-01

We show, by way of an example, that numerical bifurcation tools for ODE yield reliable bifurcation diagrams when applied to the pseudospectral approximation of a one-parameter family of nonlinear renewal equations. The example resembles logistic-and Ricker-type population equations and exhibits

Unusual Case of Overt Aortic Dissection Mimicking Aortic Intramural Hematoma

Directory of Open Access Journals (Sweden)

Kushtrim Disha

2016-04-01

Full Text Available We report an interesting case in which overt aortic dissection mimicked two episodes of aortic intramural hematoma (IMH (Stanford A, DeBakey I. This took place over the course of four days and had a major influence on the surgical treatment strategy. The first episode of IMH regressed completely within 15 hours after it was clinically diagnosed and verified using imaging techniques. The recurrence of IMH was detected three days thereafter, resulting in an urgent surgical intervention. Overt aortic dissection with evidence of an intimal tear was diagnosed intraoperatively.

Supra-aortic interventions for endovascular exclusion of the entire aortic arch.

Science.gov (United States)

Andrási, Terézia B; Grossmann, Marius; Zenker, Dieter; Danner, Bernhard C; Schöndube, Friedrich A

2017-07-01

Our aim was to analyze the outcomes of endovascular exclusion of the entire aortic arch (proximal landing in zone 0, distal landing in zone III or beyond, after Ishimaru) in which complete surgical debranching of the supra-aortic vessels (I), endovascular supra-aortic revascularization (chimney, fenestrated, or branched grafts) with partial surgical debranching (II), or total endovascular supra-aortic revascularization (III) was additionally performed. Publications describing endovascular repair of the aortic arch (2000-2016) were systematically searched and reviewed. From a total of 53 relevant studies including 1853 patients, only 1021 patients undergoing 35 different total aortic arch procedures were found eligible for further evaluation and included in group I, II, or III (429, 190, and 402 patients, respectively). Overall early mortality was higher in group I vs groups II and III (P = .001; 1 - β = 95.6%) but exceeded in group III (18.6%) and group II (14.0%) vs group I (8.0%; P = .044; 1 - β = 57.4%) for diseases involving zone 0. Mortality was higher in all subgroups treated for zone 0 disease compared with corresponding subgroups treated for zone I to zone III disease. The incidence of cerebral ischemic events was increased in groups I and II vs group III (7.5% and 11% vs 1.7%; P = .0001) and correlated with early mortality (R 2  = .20; P = .033). The incidence of type II endoleaks and endovascular reintervention was similar between groups and correlated with each other (R 2  = .37; P = .004). Type Ia endoleak occurred more often in groups II and III than in group I (7.1% and 12.1% vs 5.8%; P = .023) and correlated with midterm mortality (R 2  = .53; P = .005). Retrograde type A dissection was low in all groups, whereas aneurysm growth was higher in group III (2.6%, 4.2%, 10.7%; P = .002), correlating with midterm mortality (R 2  = .311; P = .009). Surgical revision slightly correlated with surgical complications (R 2  = .18; P = .044

A Rare Entity: Traumatic Thoracic Aortic Injury in a Patient with Aberrant Right Subclavian Artery.

Science.gov (United States)

Patel, Hiten Mohanbhai; Banerjee, Shubhabrata; Bulsara, Shahzad; Sahu, Tapish; Sheorain, Virender K; Grover, Tarun; Parakh, Rajiv

2017-05-01

Aberrant right subclavian artery is an uncommon entity incidence ranging from 0.5 to 2.5%. Management of thoracic aortic injury in the presence of such anomalies can be a challenge. We present here a case of traumatic aortic injury, which was incidentally found to have an asymptomatic aberrant right subclavian artery. The patient was managed by an endovascular repair of thoracic aortic injury with an endograft and a right carotid to subclavian artery bypass as a hybrid procedure. A 40-year male patient was brought to the emergency in shock with an alleged history of road traffic accident an hour back. After initial resuscitation as per advance trauma life support protocol, imaging revealed thoracic aortic injury with aberrant right subclavian artery with multiple rib and bilateral humerus fracture. After primary stabilization of arm fractures, the patient was shifted to a hybrid operation room. As the aortic injury was within 10 mm of the origin of both subclavian arteries, it was decided to cover the origin of both subclavian arteries and land the endograft distal to the left carotid artery origin. Since there was a right dominant vertebral artery on imaging, right carotid to right subclavian artery bypass was done with expanded polytetrafluoroethylene graft to prevent posterior circulatory stroke along with thoracic endovascular aortic repair to seal the thoracic aortic injury. After endovascular repair of thoracic aortic injury, left subclavian artery perfusion was maintained through left vertebral artery; and hence, revascularization of left subclavian artery was deferred. After management of all fractures, the patient was discharged 3 weeks after the date of admission without any complications. At 6 months follow-up, patient was stable and images showed patent bypass graft and sealed aortic injury. In a trauma setting with multiple injuries, hybrid procedure with a thoracic endograft is associated with low mortality and morbidity; hence, it is the treatment

Hopf-pitchfork bifurcation and periodic phenomena in nonlinear financial system with delay

International Nuclear Information System (INIS)

Ding Yuting; Jiang Weihua; Wang Hongbin

2012-01-01

Highlights: ► We derive the unfolding of a financial system with Hopf-pitchfork bifurcation. ► We show the coexistence of a pair of stable small amplitudes periodic solutions. ► At the same time, also there is a pair of stable large amplitudes periodic solutions. ► Chaos can appear by period-doubling bifurcation far away from Hopf-pitchfork value. ► The study will be useful for interpreting economics phenomena in theory. - Abstract: In this paper, we identify the critical point for a Hopf-pitchfork bifurcation in a nonlinear financial system with delay, and derive the normal form up to third order with their unfolding in original system parameters near the bifurcation point by normal form method and center manifold theory. Furthermore, we analyze its local dynamical behaviors, and show the coexistence of a pair of stable periodic solutions. We also show that there coexist a pair of stable small-amplitude periodic solutions and a pair of stable large-amplitude periodic solutions for different initial values. Finally, we give the bifurcation diagram with numerical illustration, showing that the pair of stable small-amplitude periodic solutions can also exist in a large region of unfolding parameters, and the financial system with delay can exhibit chaos via period-doubling bifurcations as the unfolding parameter values are far away from the critical point of the Hopf-pitchfork bifurcation.

Use of Self-Expanding Metallic Ureteral Stents in the Secondary Treatment of Ureteral Stenosis Following Kidney Transplantation.

Science.gov (United States)

Xu, Guibin; Li, Xun; He, Yongzhong; Zhao, Haibo; Yang, Weiqing; Xie, Qingling

2015-10-01

To evaluate the safety and efficacy of self-expanding metal stents in the treatment of ureteral stenosis following kidney transplantation. Seven patients who developed benign stenosis after kidney transplantation were treated by a self-expanding metallic stent implantation from June 2007 to March 2014. All patients had undergone at least one open surgical procedure and one endourologic procedure for treatment of the stenosis. The extent of stenosis varied from 1.2 to 3.7 cm. Ultrasonography, urography, diuretic renography, and urine culture were performed every 3 months after stent insertion. Ureteroscopic examination was performed when needed. Stent placement was technically effective in all cases. The mean operative time was 37 minutes (range, 26-59 minutes). Lower urinary-tract symptoms and the ipsilateral flank pain were common early-stage complications and were greatly relieved after an average of 3 months. The mean follow-up duration was 38 months (range, 13-86 months), and no stent migration or fragmentation was observed. Urothelial hyperplasia occurred in only one patient and was effectively managed with a Double-J stent. Five patients had normal stable renal function; the remaining two had impaired renal function, including one patient with a preoperative renal failure who required dialysis at the end of the follow-up period (36 months). As an alternative to open surgery, implantation of a self-expanding metal stent is a safe and effective treatment for ureteral stenosis in patients who have undergone kidney transplantation.

Use of Self-Expanding Stents for the Treatment of Vertebral Artery Ostial Stenosis: a Single Center Experience

International Nuclear Information System (INIS)

Chung, Sun Young; Lee, Deok Hee; Choi, Jin Woo; Choi, Byung Se; In, Hyun Sin; Kim, Sun Mi; Choi, Choong Gon; Kim, Sang Joon; Suh, Dae Chul

2010-01-01

To evaluate our early experience using self-expanding stents to treat atherosclerotic vertebral artery ostial stenosis (VAOS), with respect to technical feasibility and clinical and imaging follow-up results. A total of 20 lesions in 20 patients underwent stenting of the VAOS using a self-expanding stent (Precise RX; Cordis Neurovascular, Miami Lakes, FL). Two patients were asymptomatic. We analyzed the technical success rate, causes of technical failure, occurrence of any vascular or neurological event, and the occurrence of any neurological abnormality or in-stent restenosis (ISR) seen on follow-up. The imaging follow-up was performed with Doppler ultrasound (DUS) as a primary screening modality. One instance of technical failure was caused by failure of the guidewire passage. The stent diameter was 5 mm, and post-stenting balloon dilatations were necessary in all cases. Stent misplacement requiring placement of an additional stent occurred in four cases. Following a 14.8 month average clinical follow-up time, two patients showed anterior circulation ischemia, which was not attributed to the VAOS we treated. Following a 13.7 month average DUS follow-up, five patients showed a mild degree of diffuse or focal intimal thickening in the stent lumen; however, none of the stenosis showed luminal loss of more than 50% and no stent fracture was noted. The use of self-expanding stents for treating VAOS was technically feasible and helped to improve artery patency during our limited follow-up interval

Self-expandable metal stents for obstructing colonic and extracolonic cancer

DEFF Research Database (Denmark)

van Hooft, Jeanin E; van Halsema, Emo E; Vanbiervliet, Geoffroy

2014-01-01

as a bridge to elective surgery is not recommended as a standard treatment of symptomatic left-sided malignant colonic obstruction (strong recommendation, high quality evidence). 3 For patients with potentially curable but obstructing left-sided colonic cancer, stent placement may be considered......, and Evaluation (GRADE) system was adopted to define the strength of recommendations and the quality of evidence. Main recommendations The following recommendations should only be applied after a thorough diagnostic evaluation including a contrast-enhanced computed tomography (CT) scan. 1 Prophylactic colonic...... stent placement is not recommended. Colonic stenting should be reserved for patients with clinical symptoms and imaging evidence of malignant large-bowel obstruction, without signs of perforation (strong recommendation, low quality evidence). 2 Colonic self-expandable metal stent (SEMS) placement...

Aorto-right atrial fistula after ascending aortic replacement or aortic value replacement

International Nuclear Information System (INIS)

Zhi Aihua; Dai Ruping; Jiang Shiliang; Lu Bin

2012-01-01

Objective: To evaluate the CT features of aorto-right atrial fistula after aortic valve replacement (AVR) or ascending aortic replacement. Methods: Eighty-seven patients with aortic-right atrial fistula underwent CT after operation. The CT features were retrospectively analyzed. Fistula was measured according to maximum width of the shunt. Results: Aorto-right atrial fistula was detected in 87 patients after aortic valve replacement or ascending aortic replacement by CT scan. Among them, 25 patients were diagnosed as mild aorto-right atrial fistula, 47 patients as moderate, and 15 patients as severe. Thirty-seven patients underwent follow-up CT.Among them, 10 patients with mild to moderate aorto-right atrial fistula were considered to have complete regression, 8 patients with mild aorto-right atrial fistula considered to have incomplete regression, 14 patients with mild to moderate aorto-right atrial fistula considered to have stable condition, and 5 patients with moderate aorto-right atrial fistula considered to have progression at the 3-month follow-up. Conclusion: CT is a useful tool for defining aorto-right atrial fistula after AVR or ascending aortic replacement and for evaluating it in follow-up. (authors)

Traumatic Aortic Injury

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Brianna Miner

2016-09-01

Full Text Available History of present illness: A 48-year-old male with unknown past medical history presents as a trauma after being hit by a car traveling approximately 25 miles per hour. On initial presentation, the patient is confused, combative, and not answering questions appropriately. The patient is hypotensive with a blood pressure of 68/40 and a heart rate of 50 beats per minute, with oxygen saturation at 96% on room air. FAST scan is positive for fluid in Morrison’s pouch, splenorenal space, and pericardial space. Significant findings: The initial chest x-ray showed an abnormal superior mediastinal contour (blue line, suggestive of a possible aortic injury. The CT angiogram showed extensive circumferential irregularity and outpouching of the distal aortic arch (red arrows compatible with aortic transection. In addition, there was a circumferential intramural hematoma, which extended through the descending aorta to the proximal infrarenal abdominal aorta (green arrow. There was also an extensive surrounding mediastinal hematoma extending around the descending aorta and supraaortic branches (purple arrows. Discussion: Traumatic aortic injury is a life-threatening event. The incidence of blunt thoracic aortic injury is low, between 1 to 2 percent of those patients with blunt thoracic trauma.1 However, approximately 80% of patients with traumatic aortic injury die at the scene.2 Therefore it is imperative to diagnose traumatic aortic injury in a timely fashion. The diagnosis can be difficult due to the non-specific signs and symptoms and other distracting injuries. Clinical suspicion should be based on the mechanism of the injury and the hemodynamic status of the patient. In any patient with blunt or penetrating trauma to the chest that is hemodynamically unstable, traumatic aortic injury should be on the differential. Chest x-ray can be used as a screening tool. A normal chest x-ray has a negative predictive value of approximately 97%. CTA chest is the

The role of aortic wall CT attenuation measurements for the diagnosis of acute aortic syndromes

Energy Technology Data Exchange (ETDEWEB)

Knollmann, Friedrich D., E-mail: friedrich.knollmann@ucdmc.ucdavis.edu [Department of Radiology, University of California, Davis, 4860 Y Street, Sacramento, CA 95817 (United States); Departments of Radiology and Cardiothoracic Surgery, University of Pittsburgh, 200 Lothrop Street, Pittsburgh, PA 15213 (United States); Lacomis, Joan M.; Ocak, Iclal; Gleason, Thomas [Department of Radiology, University of California, Davis, 4860 Y Street, Sacramento, CA 95817 (United States); Departments of Radiology and Cardiothoracic Surgery, University of Pittsburgh, 200 Lothrop Street, Pittsburgh, PA 15213 (United States)

2013-12-01

Objectives: To determine if measurements of aortic wall attenuation can improve the CT diagnosis of acute aortic syndromes. Methods: CT reports from a ten year period were searched for acute aortic syndromes (AAS). Studies with both an unenhanced and a contrast enhanced (CTA) series that had resulted in the diagnosis of intramural hematoma (IMH) were reviewed. Diagnoses were confirmed by medical records. The attenuation of aortic wall abnormalities was measured. The observed attenuation threshold was validated using studies from 39 new subjects with a variety of aortic conditions. Results: The term “aortic dissection” was identified in 1206, and IMH in 124 patients’ reports. IMH was confirmed in 31 patients, 21 of whom had both unenhanced and contrast enhanced images. All 21 had pathologic CTA findings, and no CTA with IMH was normal. Attenuation of the aortic wall was greater than 45 HUs on the CTA images in all patients with IMH. When this threshold was applied to the new group, sensitivity for diagnosing AAS was 100% (19/19), and specificity 94% (16/17). Addition of unenhanced images did not improve accuracy. Conclusions: Measurements of aortic wall attenuation in CTA have a high negative predictive value for the diagnosis of acute aortic syndromes.

The role of aortic wall CT attenuation measurements for the diagnosis of acute aortic syndromes

International Nuclear Information System (INIS)

Knollmann, Friedrich D.; Lacomis, Joan M.; Ocak, Iclal; Gleason, Thomas

2013-01-01

Objectives: To determine if measurements of aortic wall attenuation can improve the CT diagnosis of acute aortic syndromes. Methods: CT reports from a ten year period were searched for acute aortic syndromes (AAS). Studies with both an unenhanced and a contrast enhanced (CTA) series that had resulted in the diagnosis of intramural hematoma (IMH) were reviewed. Diagnoses were confirmed by medical records. The attenuation of aortic wall abnormalities was measured. The observed attenuation threshold was validated using studies from 39 new subjects with a variety of aortic conditions. Results: The term “aortic dissection” was identified in 1206, and IMH in 124 patients’ reports. IMH was confirmed in 31 patients, 21 of whom had both unenhanced and contrast enhanced images. All 21 had pathologic CTA findings, and no CTA with IMH was normal. Attenuation of the aortic wall was greater than 45 HUs on the CTA images in all patients with IMH. When this threshold was applied to the new group, sensitivity for diagnosing AAS was 100% (19/19), and specificity 94% (16/17). Addition of unenhanced images did not improve accuracy. Conclusions: Measurements of aortic wall attenuation in CTA have a high negative predictive value for the diagnosis of acute aortic syndromes

Bubble transport in bifurcations

Science.gov (United States)

Bull, Joseph; Qamar, Adnan

2017-11-01

Motivated by a developmental gas embolotherapy technique for cancer treatment, we examine the transport of bubbles entrained in liquid. In gas embolotherapy, infarction of tumors is induced by selectively formed vascular gas bubbles that originate from acoustic vaporization of vascular droplets. In the case of non-functionalized droplets with the objective of vessel occlusion, the bubbles are transported by flow through vessel bifurcations, where they may split prior to eventually reach vessels small enough that they become lodged. This splitting behavior affects the distribution of bubbles and the efficacy of flow occlusion and the treatment. In these studies, we investigated bubble transport in bifurcations using computational and theoretical modeling. The model reproduces the variety of experimentally observed splitting behaviors. Splitting homogeneity and maximum shear stress along the vessel walls is predicted over a variety of physical parameters. Maximum shear stresses were found to decrease with increasing Reynolds number. The initial bubble length was found to affect the splitting behavior in the presence of gravitational asymmetry. This work was supported by NIH Grant R01EB006476.

3D echocardiographic analysis of aortic annulus for transcatheter aortic valve replacement using novel aortic valve quantification software: Comparison with computed tomography.

Science.gov (United States)

Mediratta, Anuj; Addetia, Karima; Medvedofsky, Diego; Schneider, Robert J; Kruse, Eric; Shah, Atman P; Nathan, Sandeep; Paul, Jonathan D; Blair, John E; Ota, Takeyoshi; Balkhy, Husam H; Patel, Amit R; Mor-Avi, Victor; Lang, Roberto M

2017-05-01

With the increasing use of transcatheter aortic valve replacement (TAVR) in patients with aortic stenosis (AS), computed tomography (CT) remains the standard for annulus sizing. However, 3D transesophageal echocardiography (TEE) has been an alternative in patients with contraindications to CT. We sought to (1) test the feasibility, accuracy, and reproducibility of prototype 3DTEE analysis software (Philips) for aortic annular measurements and (2) compare the new approach to the existing echocardiographic techniques. We prospectively studied 52 patients who underwent gated contrast CT, procedural 3DTEE, and TAVR. 3DTEE images were analyzed using novel semi-automated software designed for 3D measurements of the aortic root, which uses multiplanar reconstruction, similar to CT analysis. Aortic annulus measurements included area, perimeter, and diameter calculations from these measurements. The results were compared to CT-derived values. Additionally, 3D echocardiographic measurements (3D planimetry and mitral valve analysis software adapted for the aortic valve) were also compared to the CT reference values. 3DTEE image quality was sufficient in 90% of patients for aortic annulus measurements using the new software, which were in good agreement with CT (r-values: .89-.91) and small (software can accurately measure aortic annulus in patients with severe AS undergoing TAVR, in better agreement with CT than the existing methodology. Accordingly, intra-procedural TEE could potentially replace CT in patients where CT carries significant risk. © 2017, Wiley Periodicals, Inc.

Dynamics of the aortic annulus in 4D CT angiography for transcatheter aortic valve implantation patients

NARCIS (Netherlands)

Elattar, Mustafa A.; Vink, Leon W.; van Mourik, Martijn S.; Baan, Jan; Vanbavel, Ed T.; Planken, R. Nils; Marquering, Henk A.

2017-01-01

Transcatheter aortic valve implantation (TAVI) is a well-established treatment for patients with severe aortic valve stenosis. This procedure requires pre-operative planning by assessment of aortic dimensions on CT Angiography (CTA). It is well-known that the aortic root dimensions vary over the

Pathogenetic Basis of Aortopathy and Aortic Valve Disease

Science.gov (United States)

2018-02-19

Aortopathies; Thoracic Aortic Aneurysm; Aortic Valve Disease; Thoracic Aortic Disease; Thoracic Aortic Dissection; Thoracic Aortic Rupture; Ascending Aortic Disease; Descending Aortic Disease; Ascending Aortic Aneurysm; Descending Aortic Aneurysm; Marfan Syndrome; Loeys-Dietz Syndrome; Ehlers-Danlos Syndrome; Shprintzen-Goldberg Syndrome; Turner Syndrome; PHACE Syndrome; Autosomal Recessive Cutis Laxa; Congenital Contractural Arachnodactyly; Arterial Tortuosity Syndrome

Aortic valvuloplasty of calcific aortic stenosis with monofoil and trefoil balloon catheters: practical considerations

NARCIS (Netherlands)

S. Plante (Sylvain); M.J.B.M. van den Brand (Marcel); L.C.P. van Veen; C. di Mario (Carlo); C.E. Essed; K.J. Beatt (Kevin); P.W.J.C. Serruys (Patrick)

1990-01-01

textabstractIn order to evaluate the relation between balloon design (monofoil, trefoil) and valvular configuration, experimental aortic valvuloplasty was performed in four post-mortem hearts with calcific aortic stenosis of various morphology. The degree of obstruction of the aortic orifice was

Bunch lengthening with bifurcation in electron storage rings

Energy Technology Data Exchange (ETDEWEB)

Kim, Eun-San; Hirata, Kohji [National Lab. for High Energy Physics, Tsukuba, Ibaraki (Japan)

1996-08-01

The mapping which shows equilibrium particle distribution in synchrotron phase space for electron storage rings is discussed with respect to some localized constant wake function based on the Gaussian approximation. This mapping shows multi-periodic states as well as double bifurcation in dynamical states of the equilibrium bunch length. When moving around parameter space, the system shows a transition/bifurcation which is not always reversible. These results derived by mapping are confirmed by multiparticle tracking. (author)

Stability, bifurcation and a new chaos in the logistic differential equation with delay

International Nuclear Information System (INIS)

Jiang Minghui; Shen Yi; Jian Jigui; Liao Xiaoxin

2006-01-01

This Letter is concerned with bifurcation and chaos in the logistic delay differential equation with a parameter r. The linear stability of the logistic equation is investigated by analyzing the associated characteristic transcendental equation. Based on the normal form approach and the center manifold theory, the formula for determining the direction of Hopf bifurcation and the stability of bifurcation periodic solution in the first bifurcation values is obtained. By theoretical analysis and numerical simulation, we found a new chaos in the logistic delay differential equation

Thoracic Endovascular Aortic Repair (TEVAR) in Proximal (Type A) Aortic Dissection: Ready for a Broader Application?

OpenAIRE

Nienaber, Christoph A.; Sakalihasan, Natzi; Clough, Rachel E.; Aboukoura, Mohamed; Mancuso, Enrico; Yeh, James S.M.; Defraigne, Jean-Olivier; Cheshire, Nick; Rosendahl, Ulrich Peter; Quarto, Cesare; Pepper, John

2016-01-01

ObjectiveThoracic endovascular aortic repair (TEVAR) has demonstrated encouraging results and is gaining increasing acceptance as a treatment option for aortic aneurysms and dissections. Yet, its role in managing proximal aortic pathologies is unknown - this is important because in proximal (Stanford type A) aortic dissections, 10-30% are not accepted for surgery, and 30-50% are technically amenable for TEVAR. We describe our case series of type A aortic dissections treated using TEVAR.Method...

Three-dimensional thoracic aorta principal strain analysis from routine ECG-gated computerized tomography: feasibility in patients undergoing transcatheter aortic valve replacement.

Science.gov (United States)

Satriano, Alessandro; Guenther, Zachary; White, James A; Merchant, Naeem; Di Martino, Elena S; Al-Qoofi, Faisal; Lydell, Carmen P; Fine, Nowell M

2018-05-02

Functional impairment of the aorta is a recognized complication of aortic and aortic valve disease. Aortic strain measurement provides effective quantification of mechanical aortic function, and 3-dimenional (3D) approaches may be desirable for serial evaluation. Computerized tomographic angiography (CTA) is routinely performed for various clinical indications, and offers the unique potential to study 3D aortic deformation. We sought to investigate the feasibility of performing 3D aortic strain analysis in a candidate population of patients undergoing transcatheter aortic valve replacement (TAVR). Twenty-one patients with severe aortic valve stenosis (AS) referred for TAVR underwent ECG-gated CTA and echocardiography. CTA images were analyzed using a 3D feature-tracking based technique to construct a dynamic aortic mesh model to perform peak principal strain amplitude (PPSA) analysis. Segmental strain values were correlated against clinical, hemodynamic and echocardiographic variables. Reproducibility analysis was performed. The mean patient age was 81±6 years. Mean left ventricular ejection fraction was 52±14%, aortic valve area (AVA) 0.6±0.3 cm 2 and mean AS pressure gradient (MG) 44±11 mmHg. CTA-based 3D PPSA analysis was feasible in all subjects. Mean PPSA values for the global thoracic aorta, ascending aorta, aortic arch and descending aorta segments were 6.5±3.0, 10.2±6.0, 6.1±2.9 and 3.3±1.7%, respectively. 3D PSSA values demonstrated significantly more impairment with measures of worsening AS severity, including AVA and MG for the global thoracic aorta and ascending segment (panalysis is clinically feasible from routine ECG-gated CTA. Appropriate reductions in PSSA were identified with increasing AS hemodynamic severity. Expanded study of 3D aortic PSSA for patients with various forms of aortic disease is warranted.

Small-bubble transport and splitting dynamics in a symmetric bifurcation

KAUST Repository

Qamar, Adnan

2017-06-28

Simulations of small bubbles traveling through symmetric bifurcations are conducted to garner information pertinent to gas embolotherapy, a potential cancer treatment. Gas embolotherapy procedures use intra-arterial bubbles to occlude tumor blood supply. As bubbles pass through bifurcations in the blood stream nonhomogeneous splitting and undesirable bioeffects may occur. To aid development of gas embolotherapy techniques, a volume of fluid method is used to model the splitting process of gas bubbles passing through artery and arteriole bifurcations. The model reproduces the variety of splitting behaviors observed experimentally, including the bubble reversal phenomenon. Splitting homogeneity and maximum shear stress along the vessel walls is predicted over a variety of physical parameters. Small bubbles, having initial length less than twice the vessel diameter, were found unlikely to split in the presence of gravitational asymmetry. Maximum shear stresses were found to decrease exponentially with increasing Reynolds number. Vortex-induced shearing near the bifurcation is identified as a possible mechanism for endothelial cell damage.

Multiple bifurcations and periodic 'bubbling' in a delay population model

International Nuclear Information System (INIS)

Peng Mingshu

2005-01-01

In this paper, the flip bifurcation and periodic doubling bifurcations of a discrete population model without delay influence is firstly studied and the phenomenon of Feigenbaum's cascade of periodic doublings is also observed. Secondly, we explored the Neimark-Sacker bifurcation in the delay population model (two-dimension discrete dynamical systems) and the unique stable closed invariant curve which bifurcates from the nontrivial fixed point. Finally, a computer-assisted study for the delay population model is also delved into. Our computer simulation shows that the introduction of delay effect in a nonlinear difference equation derived from the logistic map leads to much richer dynamic behavior, such as stable node → stable focus → an lower-dimensional closed invariant curve (quasi-periodic solution, limit cycle) or/and stable periodic solutions → chaotic attractor by cascading bubbles (the combination of potential period doubling and reverse period-doubling) and the sudden change between two different attractors, etc

Small-bubble transport and splitting dynamics in a symmetric bifurcation.

Science.gov (United States)

Qamar, Adnan; Warnez, Matthew; Valassis, Doug T; Guetzko, Megan E; Bull, Joseph L

2017-08-01

Simulations of small bubbles traveling through symmetric bifurcations are conducted to garner information pertinent to gas embolotherapy, a potential cancer treatment. Gas embolotherapy procedures use intra-arterial bubbles to occlude tumor blood supply. As bubbles pass through bifurcations in the blood stream nonhomogeneous splitting and undesirable bioeffects may occur. To aid development of gas embolotherapy techniques, a volume of fluid method is used to model the splitting process of gas bubbles passing through artery and arteriole bifurcations. The model reproduces the variety of splitting behaviors observed experimentally, including the bubble reversal phenomenon. Splitting homogeneity and maximum shear stress along the vessel walls is predicted over a variety of physical parameters. Small bubbles, having initial length less than twice the vessel diameter, were found unlikely to split in the presence of gravitational asymmetry. Maximum shear stresses were found to decrease exponentially with increasing Reynolds number. Vortex-induced shearing near the bifurcation is identified as a possible mechanism for endothelial cell damage.

Small-bubble transport and splitting dynamics in a symmetric bifurcation

KAUST Repository

Qamar, Adnan; Warnez, Matthew; Valassis, Doug T.; Guetzko, Megan E.; Bull, Joseph L.

2017-01-01

Simulations of small bubbles traveling through symmetric bifurcations are conducted to garner information pertinent to gas embolotherapy, a potential cancer treatment. Gas embolotherapy procedures use intra-arterial bubbles to occlude tumor blood supply. As bubbles pass through bifurcations in the blood stream nonhomogeneous splitting and undesirable bioeffects may occur. To aid development of gas embolotherapy techniques, a volume of fluid method is used to model the splitting process of gas bubbles passing through artery and arteriole bifurcations. The model reproduces the variety of splitting behaviors observed experimentally, including the bubble reversal phenomenon. Splitting homogeneity and maximum shear stress along the vessel walls is predicted over a variety of physical parameters. Small bubbles, having initial length less than twice the vessel diameter, were found unlikely to split in the presence of gravitational asymmetry. Maximum shear stresses were found to decrease exponentially with increasing Reynolds number. Vortex-induced shearing near the bifurcation is identified as a possible mechanism for endothelial cell damage.

Period-doubling bifurcation and chaos control in a discrete-time mosquito model

Directory of Open Access Journals (Sweden)

Qamar Din

2017-12-01

Full Text Available This article deals with the study of some qualitative properties of a discrete-time mosquito Model. It is shown that there exists period-doubling bifurcation for wide range of bifurcation parameter for the unique positive steady-state of given system. In order to control the bifurcation we introduced a feedback strategy. For further confirmation of complexity and chaotic behavior largest Lyapunov exponents are plotted.

Bifurcation and synchronization of synaptically coupled FHN models with time delay

International Nuclear Information System (INIS)

Wang Qingyun; Lu Qishao; Chen Guanrong; Feng Zhaosheng; Duan Lixia

2009-01-01

This paper presents an investigation of dynamics of the coupled nonidentical FHN models with synaptic connection, which can exhibit rich bifurcation behavior with variation of the coupling strength. With the time delay being introduced, the coupled neurons may display a transition from the original chaotic motions to periodic ones, which is accompanied by complex bifurcation scenario. At the same time, synchronization of the coupled neurons is studied in terms of their mean frequencies. We also find that the small time delay can induce new period windows with the coupling strength increasing. Moreover, it is found that synchronization of the coupled neurons can be achieved in some parameter ranges and related to their bifurcation transition. Bifurcation diagrams are obtained numerically or analytically from the mathematical model and the parameter regions of different behavior are clarified.

Analysis of Spatiotemporal Dynamic and Bifurcation in a Wetland Ecosystem

Directory of Open Access Journals (Sweden)

Yi Wang

2015-01-01

Full Text Available A wetland ecosystem is studied theoretically and numerically to reveal the rules of dynamics which can be quite accurate to better describe the observed spatial regularity of tussock vegetation. Mathematical theoretical works mainly investigate the stability of constant steady states, the existence of nonconstant steady states, and bifurcation, which can deduce a standard parameter control relation and in return can provide a theoretical basis for the numerical simulation. Numerical analysis indicates that the theoretical works are correct and the wetland ecosystem can show rich dynamical behaviors not only regular spatial patterns. Our results further deepen and expand the study of dynamics in the wetland ecosystem. In addition, it is successful to display tussock formation in the wetland ecosystem may have important consequences for aquatic community structure, especially for species interactions and biodiversity. All these results are expected to be useful in the study of the dynamic complexity of wetland ecosystems.

Cardiopulmonary bypass and intra-aortic balloon pump use is associated with higher short and long term mortality after transcatheter aortic valve replacement: a PARTNER trial substudy.

Science.gov (United States)

Shreenivas, Satya S; Lilly, Scott M; Szeto, Wilson Y; Desai, Nimesh; Anwaruddin, Saif; Bavaria, Joseph E; Hudock, Kristin M; Thourani, Vinod H; Makkar, Raj; Pichard, Augusto; Webb, John; Dewey, Todd; Kapadia, Samir; Suri, Rakesh M; Xu, Ke; Leon, Martin B; Herrmann, Howard C

2015-08-01

Transcatheter aortic valve replacement (TAVR) with the balloon-expandable Sapien transcatheter heart valve improves survival compared to standard therapy in patients with severe aortic stenosis (AS) and is noninferior to surgical aortic valve replacement (AVR) in patients at high operative risk. Nonetheless, a significant proportion of patients may require pre-emptive or emergent support with cardiopulmonary bypass (CPB) and/or intra-aortic balloon pump (IABP) during TAVR due to pre-existing comorbid conditions or as a result of procedural complications. We hypothesized that patients who required CPB or IABP would have increased periprocedural complications and reduced long-term survival. In addition, we sought to determine whether preprocedural variables could predict the need for CPB and IABP. The study population included 2,525 patients in the PARTNER Trial (Cohort A and B) and the continuing access registry (CAR). Patients that received CPB or IABP were compared to patients that did not receive either, and then further divided into those that received support pre-TAVR and those that were placed on support emergently. One-hundred sixty-three patients (6.5%) were placed on CPB and/or IABP. The use of CPB or IABP was associated with higher 1 year mortality (49.1% vs. 21.6%, P non-CPB/IABP cases (53.3% and 40.3% vs. 21.6%, P < 0.001). These findings indicate that CPB and IABP use in TAVR portends a poor prognosis and its utilization, particularly in the setting of pre-emptive use, needs reconsideration. © 2015 Wiley Periodicals, Inc.

Stroke Volume estimation using aortic pressure measurements and aortic cross sectional area: Proof of concept.

Science.gov (United States)

Kamoi, S; Pretty, C G; Chiew, Y S; Pironet, A; Davidson, S; Desaive, T; Shaw, G M; Chase, J G

2015-08-01

Accurate Stroke Volume (SV) monitoring is essential for patient with cardiovascular dysfunction patients. However, direct SV measurements are not clinically feasible due to the highly invasive nature of measurement devices. Current devices for indirect monitoring of SV are shown to be inaccurate during sudden hemodynamic changes. This paper presents a novel SV estimation using readily available aortic pressure measurements and aortic cross sectional area, using data from a porcine experiment where medical interventions such as fluid replacement, dobutamine infusions, and recruitment maneuvers induced SV changes in a pig with circulatory shock. Measurement of left ventricular volume, proximal aortic pressure, and descending aortic pressure waveforms were made simultaneously during the experiment. From measured data, proximal aortic pressure was separated into reservoir and excess pressures. Beat-to-beat aortic characteristic impedance values were calculated using both aortic pressure measurements and an estimate of the aortic cross sectional area. SV was estimated using the calculated aortic characteristic impedance and excess component of the proximal aorta. The median difference between directly measured SV and estimated SV was -1.4ml with 95% limit of agreement +/- 6.6ml. This method demonstrates that SV can be accurately captured beat-to-beat during sudden changes in hemodynamic state. This novel SV estimation could enable improved cardiac and circulatory treatment in the critical care environment by titrating treatment to the effect on SV.

Bifurcation structure of localized states in the Lugiato-Lefever equation with anomalous dispersion

Science.gov (United States)

Parra-Rivas, P.; Gomila, D.; Gelens, L.; Knobloch, E.

2018-04-01

The origin, stability, and bifurcation structure of different types of bright localized structures described by the Lugiato-Lefever equation are studied. This mean field model describes the nonlinear dynamics of light circulating in fiber cavities and microresonators. In the case of anomalous group velocity dispersion and low values of the intracavity phase detuning these bright states are organized in a homoclinic snaking bifurcation structure. We describe how this bifurcation structure is destroyed when the detuning is increased across a critical value, and determine how a bifurcation structure known as foliated snaking emerges.

Nonlinear dynamics and bifurcation characteristics of shape memory alloy thin films subjected to in-plane stochastic excitation

International Nuclear Information System (INIS)

Zhu, Zhi-Wen; Zhang, Qing-Xin; Xu, Jia

2014-01-01

A kind of shape memory alloy (SMA) hysteretic nonlinear model was developed, and the nonlinear dynamics and bifurcation characteristics of the SMA thin film subjected to in-plane stochastic excitation were investigated. Van der Pol difference item was introduced to describe the hysteretic phenomena of the SMA strain–stress curves, and the nonlinear dynamic model of the SMA thin film subjected to in-plane stochastic excitation was developed. The conditions of global stochastic stability of the system were determined in singular boundary theory, and the probability density function of the system response was obtained. Finally, the conditions of stochastic Hopf bifurcation were analyzed. The results of theoretical analysis and numerical simulation indicate that self-excited vibration is induced by the hysteretic nonlinear characteristics of SMA, and stochastic Hopf bifurcation appears when the bifurcation parameter was changed; there are two limit cycles in the stationary probability density of the dynamic response of the system in some cases, which means that there are two vibration amplitudes whose probabilities are both very high, and jumping phenomena between the two vibration amplitudes appear with the change in conditions. The results obtained in this current paper are helpful for the application of the SMA thin film in stochastic vibration fields. - Highlights: • Hysteretic nonlinear model of shape memory alloy was developed. • Van der Pol item was introduced to interpret hysteretic strain–stress curves. • Nonlinear dynamic characteristics of the shape memory alloy film were analyzed. • Jumping phenomena were observed in the change of the parameters

Stability and Hopf bifurcation for a delayed SLBRS computer virus model.

Science.gov (United States)

Zhang, Zizhen; Yang, Huizhong

2014-01-01

By incorporating the time delay due to the period that computers use antivirus software to clean the virus into the SLBRS model a delayed SLBRS computer virus model is proposed in this paper. The dynamical behaviors which include local stability and Hopf bifurcation are investigated by regarding the delay as bifurcating parameter. Specially, direction and stability of the Hopf bifurcation are derived by applying the normal form method and center manifold theory. Finally, an illustrative example is also presented to testify our analytical results.

Stability and Hopf Bifurcation for a Delayed SLBRS Computer Virus Model

Directory of Open Access Journals (Sweden)

Zizhen Zhang

2014-01-01

Full Text Available By incorporating the time delay due to the period that computers use antivirus software to clean the virus into the SLBRS model a delayed SLBRS computer virus model is proposed in this paper. The dynamical behaviors which include local stability and Hopf bifurcation are investigated by regarding the delay as bifurcating parameter. Specially, direction and stability of the Hopf bifurcation are derived by applying the normal form method and center manifold theory. Finally, an illustrative example is also presented to testify our analytical results.

Aortic root reconstruction by aortic valve-sparing operation (David type I reimplantation) in Marfan syndrome accompanied by annuloaortic ectasia and acute type-A aortic dissection.

Science.gov (United States)

Inamura, Shunichi; Furuya, Hidekazu; Yagi, Kentarou; Ikeya, Eriko; Yamaguchi, Masaomi; Fujimura, Takabumi; Kanabuchi, Kazuo

2006-09-20

To reconstruct the aortic root for aneurysm of the ascending aorta accompanied by aortic regurgitation, annuloaortic ectasia (AAE) and acute type-A dissection with root destruction, the Bentall operation using a prosthetic valve still is the standard procedure today. Valve-sparing procedures have actively been used for aortic root lesions, and have also been attempted in aortic root reconstruction for Marfan syndrome which may have abnormalities in the valve leaflets. We conducted a valve-sparing procedure in a female patient with Marfan syndrome who had AAE accompanied by type-A acute aortic dissection. The patient was a 37-year-old woman complaining of severe pain from the chest to the back. The limbs were long, and funnel breast was observed. Diastolic murmurs were heard. On chest computed tomography, a dissection cavity was present from the ascending aorta to the left common iliac artery, and the root dilated to 55 mm. Grade II aortic regurgitation was observed on ultrasound cardiography. Regarding her family history, her father had died suddenly at 54 years of age. She was diagnosed with type-A acute dissection concurrent with Marfan syndrome and AAE. The structure of the aortic valve was normal, and root reconstruction by a valve-sparing operation and total replacement of the aortic arch was conducted. On postoperative ultrasound cardiography, the aortic regurgitation was within the allowable range, and the shortterm postoperative results were good.

Microarray analysis to identify the similarities and differences of pathogenesis between aortic occlusive disease and abdominal aortic aneurysm.

Science.gov (United States)

Wang, Guofu; Bi, Lechang; Wang, Gaofeng; Huang, Feilai; Lu, Mingjing; Zhu, Kai

2018-06-01

Objectives Expression profile of GSE57691 was analyzed to identify the similarities and differences between aortic occlusive disease and abdominal aortic aneurysm. Methods The expression profile of GSE57691 was downloaded from Gene Expression Omnibus database, including 20 small abdominal aortic aneurysm samples, 29 large abdominal aortic aneurysm samples, 9 aortic occlusive disease samples, and 10 control samples. Using the limma package in R, the differentially expressed genes were screened. Followed by enrichment analysis was performed for the differentially expressed genes using database for annotation, visualization, and integrated discovery online tool. Based on string online tool and Cytoscape software, protein-protein interaction network and module analyses were carried out. Moreover, integrated TF platform database and Cytoscape software were used for constructing transcriptional regulatory networks. Results As a result, 1757, 354, and 396 differentially expressed genes separately were identified in aortic occlusive disease, large abdominal aortic aneurysm, and small abdominal aortic aneurysm samples. UBB was significantly enriched in proteolysis related pathways with a high degree in three groups. SPARCL1 was another gene shared by these groups and regulated by NFIA, which had a high degree in transcriptional regulatory network. ACTB, a significant upregulated gene in abdominal aortic aneurysm samples, could be regulated by CLIC4, which was significantly enriched in cell motions. ACLY and NFIB were separately identified in aortic occlusive disease and small abdominal aortic aneurysm samples, and separately enriched in lipid metabolism and negative regulation of cell proliferation. Conclusions The downregulated UBB, NFIA, and SPARCL1 might play key roles in both aortic occlusive disease and abdominal aortic aneurysm, while the upregulated ACTB might only involve in abdominal aortic aneurysm. ACLY and NFIB were specifically involved in aortic occlusive